I did that same thing once with an older version of office.
And yes, sometimes hard to tell which PST file is which.
I copied several PST files from their residing directory to a backup folder I created. Then I opened, closed Outlook in the file I wanted to keep. I navigated to the PST file folder and checked the date and time stamp on the file. The one I just used, the one I wanted to keep, showed being accessed a minute ago. The others didn't.
This would include accessing your task or contact in that file to make sure its there.
Delete the other one or two. If you mess it up, you can copy the old files back to their original folder.
If it all works well, delete the copies you made.
It was at least 10 years ago I did this, so I'm relying on my aging memory for accuracy of what I just outlined!!