Modify nginx.conf to add nextcloud in Subdomain

I have set up two containers for nextcloud and MariaDB on my server.

Currently my server is running a meteor app using nginx on a domain like I want to know how I can modify my nginx.conf simply so, I can redirect requests for my subdomains like to the nextcloud app and make it accessible to the public so we can go to it everywhere. I was lost in the documents that I found online, so if somebody can help me, I really appreciate it.