Hope needs 2 cups to make a pint of milk since a pint is equal to 2 cups. Emily needs to buy a quart of milk since it contains 5 cups which is the amount needed for her milkshake. Sarah needs 1 gallon, 1 quart, and 1 cup of lemonade to prepare for the orders of 37 cups from 21 people since a gallon is equal to 4 quarts and a quart is equal to 2 pints or 4 cups. Farmer Dan got 14 quarts of milk from his 3 cows which is the smallest number of containers since that amount can be contained in 14 quarts.