Stretchjr - no sparc based unit has the capability to utilize 3TB drives.
Jayeyy - it is shown as dead, because when it was hot removed, the system marked it as dead. Then when you attempted to add another drive, which failed, it thinks the dead drive was put back in.
First - if you do not have a current and complet backup, this might be the time to consider doing it. Then attach the 2TB drive that is considered dead to you PC via an SATA port and using disk management, simply delete the partitions. Then try to hot add it again.
As for the 3TB drives, hopefully you can return them. If your PC is new enough to support them, you might consider using at least one for a backup target. Or, if your budget can support it, you might want to consider the Ultra 2
which from Amazon is $280. You can use it as the primary with the 3TB drives and the Duo with 2TB drives as at least a partial backup.
Remember - the NAS is not a backup plan.
Backup = Good, No Backup = Bad