Restore Library

I had a mishap and temporarily deleted my library (all fixed now), but during the panic I went to the restore button and it was greyed out, well it’s always greyed out. I have multiple back up copies saved on several other internal drives which are NFTS. Should I be saving the backup on external drives exfat ? I have created a back up on an external exfat drive, but even when this is seen by engine prime the restore button is greyed out. Finally, when making a copy of the back up do I have to zip the contents?

Thanks in advance