Reverse proxy redirect to postfix in URL

Hi

I'm completely new to Nginx and haven't had any success setting up the reverse proxy. What I need to do is redirect URLs of the form http://abcproxy.com/foo/bar to http://foo/bar. What I have right now is
server {
server_name abcproxy.com;
location / {
rewrite ^ scheme:/$uri? redirect;
}
}

I would really appreciate some help in setting this up.

Thanks