That must be a beautiful pup. Has nobody reported her missing with the dog pound?
The roundworms are common in puppies that age, and your vet will clear them up with a worming regimen. Rabbits can get roundworms if they share the same outdoor turf where dogs go potty. This is also where many dogs reinfect themselves as the eggs continue to live in the ground after being shed in their stool.

I would keep the dog separate from your rabbit until she is parasite-free at any rate, and until she knows her basic obedience commands reliably I would only allow her to see the rabbit with a gate between them.

I would not worry about her breed being an obstacle to socializing her with the bunny.

Lucky you! I’m sure she’s beautiful and very happy to have a new home.

I wouldn’t worry about the breeds – just worry about socializing her and teaching her obedience commands and you’ll be good. You can start introducing her to the bunnies once she’s parasite free if she’s on leash and the bunnies are in a cage – the more she can see them and be calm the better she’ll be once she is able to meet them face to face (when she’s older and better trained). Just make sure she stays calm and if she starts to get excited, walk her out of the room until she’s calm again, then bring her back at a safe distance where she can relax and just watch the bunnies calmly.

Labs are hunting dogs, but are trained to track and retrieve game – not kill it. It might cause her to be very interested in the bunnies at first, but I don’t think it’s likely to cause her to chase or attack them any more than any other breed. In fact, I think hunting dogs (not hounds though) are some of the best breeds to have around bunnies as they’re very trainable and it’s not in their instinct to kill (though you might have to train her not to chase or bother the bunny)

You’ll want to put up posters and search online as well. Dogs are possessions in the eyes of the law, so just like if you found money you do have to reasonably search for the owner.
Also not having ID does not make him yours-there will be a legal period where you have to try to contact them-usually a few days.
It’s not likely someone will tag or chip an eight week old puppy and likely they just got him home and he got out. Please do search for the owner. If they find you later you didn’t you could have to give him back.

IF you are comfortable sharing your state/province or country I could likely find some legal info on how long you have to search for the owners before you can claim him as yours.

As K&K stated, my first thought was to make a good faith effort to find the owner. You can also contact, or look up on line, the local government site for your city/town and contact whoever is in charge of animal control. That may be the most likely person the owner with a missing dog will contact to be on the lookout. Also, your local police headquarters may have had someone stop by asking them to watch for their dog while patrolling your neighborhoods. And of course, the nearest rescue. My downtown rescue shelter here has a listing of adoptable dogs and cats, with a separate list of missing ones with pictures. So an owner can check them online too. You can tell them, if you drop the dog off with any of the rescues, that you want him if he is not claimed within a certain time. As K&K said, there’s usually a legal limit before it is OK to keep a dog, but you need to try.

If you are concerned that the dog was abandoned and has the ringworms due to neglect, and the owner is found, that may mean the city can slap a fine on those people, too, and you still can keep the dog. So they will be less likely to go out and get another.

Definitely keep the dog away from the bunnies for the duration of the ringworm treatment and use the time for the search and training. You might end up returning a better dog to the owners than the one they lost, but they could be asked to reimburse you for the vet bills also.

ringworm is a fungal infection and can be transmitted from humans to pets and vice versa.

pinworms are different than roundworms.  rabbits usually have pinworms- dogs and cats usually have roundworms.  But there are different types of pinworms and roundworms- and I believe all are transmittable to humans- and often more devastating to the health of the human since it is not their regular host- the parasite gets confused and burrows in other areas- for example- the eye- which can result in blindness.  Usually this stuff happens to kids as they have less than ideal hygiene compared to an adult.

It is not possible to tell which species of roundworm it is unless you prepare a sample to look at under the microscope and identify which type of eggs are being passed in the stool.  But usually the general diagnosis of roundworm is made- not the species as that is pretty specialized and will not make a difference in meds- all round worms meds will treat all roundworms.

So there are some types of parasites that are or are not zoonotic (can affect people)- but it is always important to quarantine any new pet whether you see parasites or not as some are not visible to the naked eye (like coccidia) and if you can see one parasite- like a roundworm- they can have more than 1 parasite.