Matter from a Black Hole doesn't "go" anywhere. It was deemed a "black hole" because it's escape velocity is greater than the speed of light therefore light can't even escape. In reality black holes objects, collapsed stars to be specific, sucking in everything that gets too close and crushing it with it's immense gravitational pull. It is said that nothing can escape a black hole because Einstein's Special Theory of Relativity tells us that Newton's Law of Inertia only applies to objects with relatively slow velocities. Once an object nears the speed of light it requires more and more force to accelerate said object until it hits the speed of light which requires an infinite amount of force. Since nothing can apply an infinite amount of force nothing can accelerate past the speed of light and since the escape velocity of a black hole is greater than the speed of light nothing can escape.
The matter from a black hole doesn't "go" anywhere. A black hole isn't a hole. It's called a black hole because it appears as such since the escape velocity is greater than the speed of light. Since this is the case light cannot even escape the gravity of a black hole. All matter from a black hole is simply crushed from the immense gravitational pull.