My external hard drive seems to be empty. I need help figuring out where all my pics are.

Fat32 will work with both. It seems as though one or the other of the computers has “initialised” the drive. It will sometime suggest that immediately after connection. You will need to run a file recovery app. The one that comes with many SD cards will often do when used on an external drive,

Hook it up to your PC and run the utility Chkdisk on the drive. (Right click on drive-letter, properties, tools, check disk for errors.)

Did you use an included software with the hard drive to backup data from the Pc? If thats how you backed up those pictures, I would wager it’s the reason you can’t find them. Try the click and drag method.

And as mentioned above, FAT32 is compatible with both OS’s