Thinking: this question is about length, width and square, and it should be said that it is a rectangular area.
The units of length and width are meters, so there is no need to unify the units, just multiply them directly. Calculation formula:
140x4
=560 square meters
Length140m, width 4m, 560m2.
1 square is 1 square meter, which is commonly known as 1 square meter.