help organizing my hard drives for recently completed project

I've acquired some bad habits in teaching myself FCPX.
Afraid to delete files, I've just been filling-up one hard drive after another with various versions of my short film.
Now need to free-up those hard drives and get it all down to one or two drives. But I'm afraid to touch any of the files for lack of understanding of FCPX file management... Help!

Unfortunately you'll have to know how you managed your projects.
When importing files into FCPX you can "Leave them in place" or import them into an FCPX Library.
You may need to open FCPX and see where the files are for each project.
Personally I'd never delete source files. I don't delete Libraries either. I just buy more hard drives.