
A 6 week old pup would still be with it's mother, being fed on what it was weaned onto with top ups of it;s mother milk.
Sadly your breeder who should be the person to guide you in this is obviously not reputable.
The puppy at this age will probably need a minimum of 4, and maybe 5 or 6 meals a day of easily digested food. I suggest as you are inexperienced that a dry complete puppy food of better quality is used.
Something like Arden Grange Puppy, James Well beloved Puppy. Stay away from foods with bright colours and fancy shapes. In my view mist tinned food is best avoided as often will give upset tummies, and really smelly poos. the pouch type foods are a little better as an appetiser added to the dry food for pickier pups.
How did you find your breeder? If they were commercial and require a licence (breeding five or more litters in any 12 months) then they would have been breaking the law selling a pup under 8 weeks old.
Most good breeders agree that between 7 and 8 weeks is absolutely the youngest pups should be homed,a nd in some breeds longer.