Compare External Hard Drives

I have 3 external hard drives from past 3 years and want to compare contents and then consolidate data. After that I would reformat one of the external drives to use for current backups. Any program available for this?

Would these drives happen to have different versions of the same files? Or are they all just various different files?

Are you saying that all 3 dives have buun used for Time Machine backups and you want to see what's in the backups themselves?

Would like to combine files to one drive.

Not so interested in seeing what's in Time Machine or my other backup program, Super Duper. There's mostly duplicated files on these drives and would like to easily combine onto one drive or two drives without manually picking and choosing what to erase due to duplication, which is in some instances older files backed up on 3 separate drives. Would like to know if there's a program that can scan the drives and give me list up duplicates or perform the task of consolidation. Thanks