Shortlink /?p=ID# not working for pages

Hello,
I am having a major issue with redirects.
I was told to use a regular expression that would handle many of my redirects by redirecting to /?p=ID#. The issue is that it works for posts but not pages.
So I tried changing it to /page_id=ID# but that seems to only work for pages and not for posts.
I am not sure what to do, and this is getting quite urgent for me because my site has been generating thousands of 404’s since I migrated from Joomla to WP, which I gather is not got for my search engine rankings.

Is there a shortlink that works for both pages and posts? And if not, how do I handle redirects based on the ID when the ID might from from either a page or post?

Thank you.