I have to make a solar system model for school, and I have to put the kuiper belt and asteroid belt in with it, I have no idea how to put the belts in. Also I have a set that has styrofoam balls and the planet stick out of the sun with wires. Also What could I use to make the belts?

Maybe some thin gauze on a wire hoop?

you should also include the oort cloud and the nearest galaxy. that way everything else just becomes a dot :0)

Or maybe a stocking with some pebbles randomly glued to it. The mesh of the stocking could be the dust and the jagged pebbles the larger objects.

If you're doing that on a flat surface, some sand would do fine!