where does somthing end up when it is sucked into a black hole?

Answer 1

Its mass is added to the black hole.
Once inside the black hole, gravity is too strong for anything, even light, to escape. Matter that enters a black hole has effectively isolated itself from the rest of the universe - forever.

Answer 2

It becomes part of the mass of the black hole - part of the singularity. It doesn't 'go' anywhere.