Can anyone recommend a PC program that will look for duplicate files on a set of hard drives?

I have been creating files related to my hobby since 2001. I have burned a back up to CD every year. I want to copy each CD to a separate directory on a hard drive and then compare the directories so that I get the last version of each file which can be copied to another clean directory.
I know that the latest backup “should” have the most recent files but that is not the case for various reasons.
This is a Windows-PC. Looking for freeware.

Any suggestions and thanks to all