Rick is backing up his photos and after formatting the drive, his Mac can't see it anymore. Leo says it sounds like Rick formatted for the wrong format. He wants to re-format it with exFAT. That makes it readable on both macOS and Windows. Also, choose MBR compatibility or GBT. There's also a utility called PARAGON and FUSE that will teach the Mac to write to NTFS. But reformat that drive in exFAT and you should be OK. It may also be that Rick partitioned the drive, but didn't format it. You have to do both.