Do you guys know what dog breed he is?

We can tell you for a fact, he is NOT a purebred of any kind.  (This is a mix of several breeds.) 

Mixed breed! And, soooo cute! Probably a Jack Russel Terrier mix.

None in particular, likely a mix of several or more breeds. He has no characteristics that would point to any specific breed being part of the mix.

I think he's a really cute mixed breed.

He looks like a Jack Russel Terrier.

Looks like a healthy, but somewhat anxious little guy.
I'm guessing not poodle.

I don't recognize any specific breed, so it has to be mixed with several different breeds.  A BYBed pup for sure.

A Jack ace breed

I got a big strong American Staffordshire bull terrier can kill your dog easy. 

looks like a jack russell terrier to me.

A mutt, that looks like it has a good deal of hound in it!

I'm not sure but he sure is cute

its beagle mix 

i would ask your vet