Which scaling system should be used in box2d?

Box2D is tuned to MKS devices. Keep the size of moving objects approximately between 0.1
and 10 meters. You must use a scaling system when rendering your image
Environment and actors. The Box2D testbed uses an OpenGL viewport to do this
turn. DO NOT USE PIXELS.

I do not want to use openGl because I do not know about it.