Answer: He can make 48 batches of muffins.
Explanation:
Hi, to answer this question we have to convert the gallons into cups. 
First, we have to convert the gallons into quarters. 
Since 1 gallon = 4 quarts 
3 gallons of milk are equal to: 
3 gallons x 4 quarts/gallon = 12 quarts 
Since 1 quart = 4 cups 
12 quarts of milk are equal to: 
12 quarts x 4 cups /quart = 48 cups 
Since he needs 1 cup of milk for each batch of muffins he make, he can make 48 batches.