Trying to mod_rewrite for specific files

Hello all,

Using a .htaccess file, I am trying to get a few specific files on my server to rewrite their URLs to contain “https://” at the beginning, for a secure connection.

I am using this code elsewhere

RewriteCond %{SERVER_PORT} 80
RewriteCond %{REQUEST_URI} admin
RewriteRule ^(.*)$ https://www.<Site URL goes here>/admin/$1 [R,L]

To add the https for any file in that directory.

However, I have no idea how to apply this kind of action for specific files in a directory. And regular expressions have me very confused.

Any help is appreciated,
Thanks