I normally don't help wih homework but this is hard at best.
First there is no real count. So any number is just a guess.
And what is slave labor or sweat shops to one group may not be to antoher. some civil rights group calls some of the work done by teens in the US are consider child labor to them.
But this web site
Child Labor Throuhghout the world
says that there are about 250 million children in slave labor and sweat shops. and about 60 percent of them are in China.