A square has four sides, a plane has two sides, and a cube has six sides.
You're messing up your terminology. Also, are you talking about line segments or faces?
If you're talking about faces:
A cube has 6 faces, a square has 1 face and a plane has 0 faces.
If you're talking about line segments:
A cube 12 line segments, a square has 4 line segments and a plane has 1 line segment.