Your training calls for 4x4 hill repeats. This equates to 3 miles. If you've never done hill repeats here is a description of them.
Hill Repeats: 1 - 2 mile warm up. Find a hill about about an 1/8 mile uphill. Run
up the hill and recover when you come back down (a slow jog). Repeat the hills (this week calls for 4 times) and after the hills run 1 - 2 mile cool down. Don't choose a hill that is super steep. Try to find a hill with 10 -15 % grade.