I found a puppy in my backyard which doesnt seem to have an owner. My question is if there would be a problem bringing him in to the shelter unvaccinated? Dont know his whereabouts. without him being vaccinated? his whereabouts

Yes. Take puppy there. However, you might ask around your neighborhood first in case one of your neighbors lost the puppy. Many people use apps like Nextdoor and Craigslist to let neighbors know their pet is missing, also. If I find a cat or dog, I would take the animal's picture and post it on Nextdoor in their Lost and Found category and wait a day for replies. I have found two owners of cats that way.

I think you can just let them know the info you just stated and they will go from there many animals are taken there

You can bring him in without vaccinations. I just took a puppy there I found, I ended up fostering her for a week, they supplied me with dog food & Frontline flea preventative. The vet will give puppy vaccinations, spay/neuter before putting him in adoption kennel. Hope this helps