We have two 1TB Seagate external drives.  One is the main drive and the other is to be the backup.  The software that comes with the drive will not allow me to backup from a removalable USB drive.  I have been on google and tried three, but issues with licencing and one made huge zip files.  I just need one that copies the files (flat) onto the other drive, but keeps a track of the files to manage duplicates and changes etc.  I did have an old Seagate backup for Windows XP (back in the day) that did do this.   I'm using Windows 10 Backup already that backs up the computers documents etc onto another external drive.

What software is about that works in this case?

Mike