How to make bulk changes to wordpress posts

Why not change your site’s htaccess file to include this code

RewriteEngine On
RewriteCond %{SERVER_PORT} 80 
RewriteRule ^(.*)$ https://www.example.com/$1 [R=301,L]

…changing to your domain name. This takes all port 80 requests (http) and rewrites them to https.

Then, make sure that the wp_options table has the https URL for your site in both locations.

There are also plugins that will do this for you.