what's wrong with my nginx reverse proxy configuration?

location/merchant/mangooda 
   rewrite /merchant/mangooda / break;
   proxy_redirect     off;
   proxy_set_header   Host $host;
   proxy_pass http://localhost:9001;
}

This is my nginx configuration. I want to get the localhost:9001 when I go to the server_name/merchant/mangooda. But now when I go to the 'server_name/merchat/mangooda', it's going to the localhost:9001/merchant/mangooda. This path does not exist in localhost:9001. So, I got 404 error. Can anyone fix my problem?

In case 'proxy_pass http://localhost:9001/', when I change the proxy_pass like this, url is working but it doesn't load CSS contents in my NodeJS app. only showing HTML pages.