Why do you use cubic units and not square units to find the volume of solid figures?

Let's say you have a (1 unit) by (1 unit) by (1 unit) cube.

The Volume of this cube would be (considering a unit=u):

V=(1u)*(1u)*(1u)

=1*1*1*u*u*u

=1u³

The volume of this cube would be 1 unit^3 or in other words, 1 unit cubed.

--------------------------------------------------------

These solid figures are 3 dimensional entities. 3D shapes are made up of 3 elements: length, width and depth. Length, widths and depths are each 1 dimensional entities. Lengths emerge as points are dragged across a certain distance. Areas emerge as lengths are dragged across a certain distance. Volumes emerge as areas are dragged across a certain distance.