Setup a FTP server for MKSBackup and connect it to the USB drive.

MKSBackup has a built-in FTP server but it didn’t work that well so my choice for this experiment was to use FileZilla.  Download the FileZilla ftp server for Windows: FileZilla Server
1. Install FileZilla
2. Let FileZilla start as a Service
3. Open the FileZilla Server Interface and navigate to Edit -> Users

4. Create a new user ( I named it ghetto ) and set a secure password. (leave  this windows open)

5. Navigate to Shared folders, Click Add for a new home Directorie.
6. Navigate here to the back-up folder on the USB drive and hit OK.
7. Mark all the options  for Files and Directories.
8. Select the USB drive and click on Set as home dir, after that you can hit the ok button on the left en close filezilla.

If you have problems with the USB drive because it keeps changing the drive letter, read the following post:  USB Drive Letter Manager