If these are older than (say) 5 years most of the data is "stale"--probably a simple pass or two of a drive erase utility should be sufficient.
Another option is to pull the drives and use them externally (adding a drive enclosure) for back-up purposes.
About 5 years ago my pc was "scammed": "we're from Microsoft and we detected 'bad files' on your computer" the scammers got onto to my computer and "showed me bad stuff", I detected a scam and wanted them off my system, they "sysgened" my system, since the computer was getting flaky I pulled the drive backed it up to a new computer...in 5 years I've never needed to access any of the backed up dats.