I'm 10 I'm getting therapy for self harm and I'm scared to go because I heard that they can send you to a mental hospital if your capable of harming yourself.

A therapist cannot divulge anything you tell them to anyone, unless they have reason to suspect that you're a threat to yourself or others.

Be honest with the therapist. If you're self harming you need help. You won't get that help if you're not straight forward about what's going on.