Unless I’m misunderstanding what it is you want to do, this isn’t something that can be done with ACF. It could be done, but you’re talking about linking content entered into a content editor and automatically linking that content to another post. What you need here is to add a filter on “the_content” (https://codex.wordpress.org/Plugin_API/Filter_Reference/the_content) that searches the content, finds the reverences and then adds the links, all of which would undoubtedly slow down your site as you get all the links and then search for each of the things you want to link.
