How to use proxy_pass to redirect in Nginx config and how to set 443?

I have aqueduct server running on 127.0.0.1:8000 and I install nginx following h****s://certbot.eff.org/lets-encrypt/ubuntubionic-nginx commands.

When I run 127.0.0.1 I get static index.html that shows nginx welcome’s page. In my sitesi-available I have default file that pre config from nginx.

My domain name is mine.example.com . when user types mine.example.com I need to show default nginx index.html.

But if users types mine.example.com/login than I need to redirect to my dart server (which currently running on 127.0.0.1:8000).

if user types without s h**p://mine.example.com I need to show a default nginx index.html.

other than that everything must be redirect to (h ps://mine.example.com/* ) 127.0.0.1:8000.

How to use proxy_pass to redirect in Nginx config and how to set 443?

How is this question different from what’s being asked here:
https://community.letsencrypt.org/t/how-to-redirect-404-to-deafult-index-html/95759/3
…and what do either of them have to do with using the Let’s Encrypt services?