My family shunned me. How can I replace them?

You can't. No one can replace your family. But you can surround yourself with positive people. Maybe going to a church or a community center or a support group in your community would help. Or you might want to consider talking to a counselor about how you are feeling. Being shunned hurts. You shouldn't be alone with those feelings.
Good riddance. Harsh but true. There are many situations in which you're best without any contact with a dysfunctional family of origin. "shunning" is a practice used by authoritarian cults in which members are forced to break all contact with a "sinner" even in their own family -- for example a jw who accepts a transfusion. The key is friends -- find activities u truly enjoy, be polite & helpful. It'll be good.