HTTP to HTTPS

From how can I rewrite all http requests to https

http {
    include /etc/nginx/mime.types;

    server {
        listen [::]:80;
        return 301 https:/$host$request_uri;
    }

    server {
        listen 443 ssl;

        ssl_certificate /srv/ssl/ssl-unified.crt;
        ssl_certificate_key /srv/ssl/server.key;