I'd like to say that we need to draw a square of which each edge length is 10 cm (i.e., 100 square cm).

What is the simplest way to represent such shape? Is the following sentence makes sense?

We need to draw a 10-cm rectangle.

We need to draw a rectangle each side 10 cm.

I think this is a very boring and childish question. However, this kind of simple thing is sometimes difficult for non-native English speakers. Please help.