To convert quarts to gallons, you need to know that 1 gallon is equal to 4 quarts.
To find out how many gallons Sara needs, you can use the following calculation:
\[ \text{Gallons needed} = \frac{\text{Quarts needed}}{\text{Quarts per gallon}} = \frac{56 \text{ quarts}}{4 \text{ quarts per gallon}} = 14 \text{ gallons} \]
So, Sara needs to buy 14 gallons of milk.