The area of the parallelogram is 96 square miles. find its base and height.

You can't. There are an infinite number of different parallelograms,
with different dimensions, that all have area of 96 square miles.

Knowing the area doesn't tell you the dimensions.

Here are a few parallelograms with areas of 96 square miles:

-- square, every side  4√6  miles long

-- rectangle, 12 miles long, 8 miles wide

-- parallelogram, base=32 miles,    height=3 miles

There are an infinite number of others.