You have to reformat them (or one of them) to FAT32 for use with a B2.
NOTE! reformatting a drive will cause loss of all data previously on that drive - so make sure that there is nothing you want to keep on it before you do this.
To reformat an NTFS formatted drive to be FAT32 format, Use the B2 to achieve this.
Plug the drive into USB pot A on the back of the B2
Go to the front screen and using this and the round knob use the menus thus
"Main Menu > Settings > Maintenance > Format USB "
Fred