The site should link to the URLs you want users to see and use. URLs are defined in links.
htaccess cannot "make" URLs. This part of the solution needs changes to the Wordpress configuration and code.
You then need a RewriteRule configured as a rewrite to connect the URL request after a link is clicked with the internal filepath where the content really resides.
You also need a RewriteRule configured as a redirect so that users asking for the old URL when clicking stale searchengine listings or bookmarks are redirected to the new URL.