Thank you for your response Monicabang - much appreciated.Here are three ways to format a WD My Passport, follow any one of them to convert to FAT. If you want to share digital files between Mac and Windows system easily, you must convert WD My Passport to FAT or exFAT.

That is to say, only FAT32 and exFAT can work on both Mac and PC. In addition, the ReFS file system was developed as a new generation file system for server computers starting from Windows Server 2012. FAT was inherited from old DOS and has exFAT as its later extension. While Windows employs two major file systems: NTFS and FAT. macOS supports a handful of common file systems - HFS+, FAT32, and exFAT, with read-only support for NTFS.