You are correct about not being able to destroy matter. However, Einstein showed that matter can change states and become pure energy with his famous E=MC2 formula. It is why nuclear bombs are so powerful. If you believe in physics and the Big Bang theory, we all came from an exploding star and were just pure energy. That energy became matter over time and what we are today. A black hole would reverse things and eventually turn us back into pure energy.
If you entered a black hole, once you got in, you would eventually reach something called the "event horizon," which is the point where it is impossible to escape out. Not even light can leave the event horizon because gravity is so strong. After that, you would get stretched from head to toe and torn apart from the strong gravity pull. You would look like toothpaste coming out of a tube. Next, as the stretching got stronger, you would become a stream of electrons traveling towards the center of the black hole getting denser and denser as you got closer to the center. You would obviously not survive it and probably pass out very quickly once you entered the black hole. Your body would become pure energy and be compressed to the smallest space you can imagine.
