The problem is, the hard drive partitions are formatted using the UFS standard which Linux Mint cannot use. My computer with Linux Mint uses the EXT4 standard.
Thankfully there is a BASH work around, Linux will READ but cannot write to these drives. So here I used a HDD docking station -
sudo mount -t ufs -o ro,ufstype=ufs2 /dev/sdc2 /mnt/Now I can read/copy the files to another location before reformatting the drive with ext4 (or FAT32 for windows). Note pay special attention to the error that comes up on the monitor, this tells you the actual mount name you have to use, in this case it is sdc2. Last time I tried another HDD, itcame up as sdc1, all depends on how many usb devices you have connected at the time.
Hindsight ... I really need to rebuild a new NAS setup .. pref with an i5 intel processor and 4x 4TB HDD's.