At the present time, how many extra-solar planets have had confirmed discoveries?

Well, it really depends on your information in the book, given that this data is constantly changing, every day new extrasolar planets are discovered.
According to the Internet, at the present time (as of 22 January 2017), there are 3,565 exoplanets in 2,675 planetary systems. 

Don’t use up to much of them it leads to pollution

Magma forms by partial melting of upper mantle and crust. partial melt means that only a fraction of the available material forms a melt, and that the remainder stays solid. the partial melt rises because of its lower density and ascends through he crust. this is so conclusive mean the answer would be magma igneous rocks or balistic magma.