This question has already been answered, but 1 acre is equivalent to .0015625 square miles.
640 acres
0.0015625 mi², algebraic steps below: 1 acres*1 mi² 640 acres=0.0015625 mi²
One square mile equates to 640 acres.
This question doesn't make sense and can not be answered - because a mile is a measure of distance, whereas an acre is a measure of an area.