Why can you not find the volume of an circle by multiplying the length by its width by its height?

A circle is not three-dimensional. It is a two-dimensional shape than can have an area, but not a volume. A column or cannister would have calculable volumes because they are three-dimensional shapes.

To find the area of any circle, just remember 'Pie are square'. Of course, everybody knows that cakes are square and pies are round, but this is a different sort of pie. It is actually spelled pi. And the 'are' is actually an 'r' to signify 'radius'. In math, when we 'square' something, we are multiplying it by itself.