How do i find this missing measurement?

The area of a parallelogram is equal to the base times the height.

In terms of algebra
A = b*h

We know the base is b = 8.2,the area is A = 65.6, though we don't know the height h. We can use algebra to solve

A = b*h
65.6 = 8.2*h
8.2*h = 65.6
8.2*h/8.2 = 65.6/8.2 <--- divide both sides by 8.2
h = 8

The height of the parallelogram is 8 inches