Try this for a complete site wide redirect to HTTPS://
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
All older pages should be caught under this rule.
Also remember to update your Search Console profiles, sitemap etc
Update any hard-coded links or blocking rules you might have in your robots.txt that might still be pointing to HTTP directories or files.