
All you can do is try the new food,don't buy a big bag in case it doesn't suit, see if you can get samples to try.
Leave the pup on the old food for a few days after arrival as you don't want to upset its stomach whilst it is settling in and getting used to different drinking water and new home etc.
Then over at least a week change over to the new food and an increasing amount each day till they are just on the new stuff.