Also you can't mirror 2 drives to 1.
A mirror is 1 to 1 and will act as 1 drive. You can mirror 3 drives but again they will act as 1 drive, not 2 or 3. So for example, you mirrored the ssd to the 1tb to the 2tb you would end up with one drive, 250gb in size (Raid uses the smallest drive size) and each drive would be an exact copy of the SSD. The rest of the space on the Hard Drives would not be usable normally.
A higher end raid controller card would let you but that is probably above your ability currently.
As for backups, any important files (music, videos, pictures, game saves...) that you dont want to lose you need to have backed up. All drives fail eventually and having those files backed up to something else is the only way to survive it.