I could just keep guessing until I get it right. It is a number between 0 and 10.

I know there are 3 for sure in the brinstar
1 in the wrecked ship
1 in the crateria
1 in the Meridia

I know I am missing some from those areas so that really levels it down to 0-4

So I guess 3 now. It is only a matter of time