nginx ProxyPassReverse | Talk Web Hosting

I have an Apache server on which I use the ProxyPassReverse feature to forward web requests from my server to an external server. I put the following
configuration in the httpd.conf file:

ProxyPass / smsprox http://sm.incomingsver.com/send
ProxyPassReverse / smsprox http://sm.outgoingsver.com/send

What should I do to get there on the nginx server?