There are probably a hundred articles that tell you how to change your Joomla settings to remove the /index.php/ from your links, but not a place to show you how to properly redirect existing indexed URLs to the new variant. Add the below code to your .htaccess file. If you already turned on the “Use URL Rewriting” feature, then it is already in your root folder of your Joomla website.
RewriteEngine On
Remove from middle of url
RewriteEngine On
RewriteCond %{REQUEST_URI} ^/index\.php/
RewriteRule ^index.php/(.*) /$1 [R,L]
Remove from end of url
RewriteEngine On
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /(.*)index\.php($|\ |\?)
RewriteRule ^ /%1 [R=301,L]
