How do I format WD easystore to accept .dav files?

Hello. I am trying to back up CCTV files onto my WD 4TB easystore. The file type is .dav. ADT technical support said the portable hard drive had to be formatted to accept the .dav files. When I try a standard USB flash drive, it works flawlessly. Anybody know how to get the easystore to recognize this file type to save?

Formatting the hard drive will not change what type of file extensions can be copied into it, but rather from where. Where are you trying to connect your hard drive into? A DVR or a TV will require for your hard drive to be formatted as FAT32 while Windows will use NTFS and a Mac HFS+.