How do I setup a reverse proxy on Cloudflare?

server {
  listen 80 default_server;
  client_max_body_size 100M;
  server_name <your domain (optional)>;
  
  location / {
    proxy_pass http://localhost:3000;
    proxy_set_header Host $host;
    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;
  }
}

server {
  listen 80 default_server;
  client_max_body_size 100M;
  server_name <your domain (optional)>;
  
  location / {
    proxy_pass http://localhost:3000;
    proxy_set_header Host $host;
    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;
  }
}

fetch(request) {
    const url = new URL(request.url)
    url.host = "149.56.67.129:25585"
    return fetch(url, request)
}

fetch(request) {
    const url = new URL(request.url)
    url.host = "149.56.67.129:25585"
    return fetch(url, request)
}

fetch(request) {
    const url = new URL(request.url)
    url.host = "149.56.67.129:25585"
    return fetch(url, request)
}

fetch(request) {
    const url = new URL(request.url)
    url.host = "149.56.67.129:25585"
    return fetch(url, request)
}