1 gallon = 4 quarts
1 quart = 2 pints
1 pint = 2 cups
So 2 pints = 4 cups = 1 quart
4 quarts = 4 cups * 4 quarts = 16 cups
16 cups = 1 gallon
To better remember how many cups are in a gallon or quart or whatever, you can search google "super gallon man"