it is unknown for now, but scientists do know that there are hundreds, or possibly thousands.., or even millions! they come in so many sizes, and it is difficult to count them and it is nearly...
Seeing as noone we know has explored the entirety of space, we cant' be sure. We DO however know that there is only one in our solar system.
Scientists have estimated that over 24,000,000 astroids and meteors are in the asteroid belt
the Asteroid belt has no satelites all the asteroids that make up the belt is another asteroids satelite so there would be thousands of satelites