301 Redirect is great, if you want to keep you old structure and only change the server.

.htaccess

Redirect 301 / https://www.trembl.org/

Any page of your old.site/about would get redirected to https://www.trembl.org.about

If you want to redirect all your page links from your old.site (e.g. old.site, old.site/aaa, old.site/bbb, …) to https://www.trembl.org, use this RewriteRule:

.htaccess

RewriteEngine On
RewriteRule ^(.*)$ https://www.trembl.org/ [R=301]