Nginx – hide port in ngnix and display site-link instead

I have already tried suggestions mentioned in:

Hide port in Nginx reverse proxy redirection

but it does not help me.

I have done nginx reverse proxy for my django+gunicorn application and it is open on port 8000. I can access a machine name as http://some_machine:8000 to see my app running. I have mapped localhost running on that machine with machine name using Nginx reverse proxy. I want to hide the port and in url would like something like http://some_machine/zmk instead of http://some_machine:8000/zmk.

I am writing the below content to my /etc/nginx/conf.d folder:

upstream zms {    
  ip_hash;    
  server zms:8000;    
}

# portal

server {    
  location /zmk {    
        proxy_pass http://zms/;    
        # proxy_redirect http://some-machine:8000/ http://some-machine/zmk;    
        port_in_redirect off;    
        # autoindex on;            
        proxy_set_header Host $host:$server_port;    
        proxy_set_header X-Real-IP $remote_addr;    
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;    
        proxy_set_header   X-Forwarded-Proto $scheme;    
    }
  listen 8000;    
  server_name localhost    
  server_name_in_redirect off;    
}

I am not understanding what am I doing wrong? I have also tried copying the above content to /etc/nginx/site-available folder.