Custom Integration Advice

Hello all-

I’m trying to use WordPress as a CMS for this site:
https://www.miltons-atl.com/newsite/sub.php?page=60

The issue I am having is with the links…

I need them to link back to this page but I can’t figure out how to change the path to something like this:
https://www.miltons-atl.com/newsite/sub.php?page=60&page_id=2

I’m actually not sure if this is the best way to handle this project, so any advice or feedback is greatly appreciated.

Thanks much!