However, this may not be an issue with .php files. if you load the page in question, and the page source (usually displayed by pressing Ctrl-U) does not contain the HTML you see when inspecting an element, it means the HTML was added with javascript. If this is the case, you’ll need to modify a .js file.

WordPress 4.9 wisely added a warning that one should not edit theme or plugin files using its built-in editor. (I personally hope this is a prelude to the theme/plugin editor being completely removed from WordPress.) Please heed that warning and edit the files outside of WordPress, most likely via FTP. Editing a .php file incorrectly can break your site, which means you cannot use the built-in editor to fix your mistake!

You could alter the theme template responsible for this output so it links to something besides the permalink. Or you could change the destination page that is queried so it has the content you really want linked to. The excerpt can remain as it is, but a custom page template could be built to have any kind of content you want.

You could completely replace the dynamic query and loop for static content. It’s very poor practice to hardcode content right on a template, but it’s an easy solution. You could replace the current query and loop with different code that gets the desired content from elsewhere, like custom fields of a specific page. Then the links could be updated by editing custom fields instead of editing template files.

It doesn’t have to be custom fields either, it could be custom options for example. Or you could simply filter the output for the_permalink() when the call is for one of these three pages. The link could still come from any number of places or be hardcoded in the filter callback. There are all sorts of approaches you could use, it depends on how you want to manage the content that’s output.

You’ve seen how cryptic it can be coming into a theme cold and trying to find the source of specific content. Keep this in mind when deciding which approach to use. Will it be easy to figure out when you return to change something a year later? Would someone else coming to the site cold be able to intuitively find the source without a lot of digging?