If its a thread you created or posted in you can find them by clicking on your username at the top which pops out a drop down menu, click again on your username which brings you to your profile page. Click the green find box above the blue bar which drops down a menu with options to 'find all content' or 'find all threads'.I've save a few links to different parts of the forum. Since the forums changed to the new setup those links no longer work. I take it that I'll have to dig up the threads and save it all over again or is there a better way to recover the old threads?
'Find all content' will bring up posts you replied to and 'find all threads' brings up threads you created.
However once you find a thread you should compare the new URL to the old one. Fixing it may be as simple as changing the /forum/ to /forums/ as some of the formatting has changed slightly.