ASK NC

I have subscribed to your channel for nearly 2 years and bought a TerraMaster F5-221. with two Seagate IronWolf 10TB NAS Hard Drives and I think I have set it up as Raid 1.
Being a newbie to NAS I thought that I would be able to add more storage as and when I needed it, I save Old Time Radio Broadcasts and have a collection dating back to 1920’s. I now have only 5% left and I wish to increase my storage. Can I add 2 x 14Tb NAS drives on top of the ones I have? Or will I lose my data from the original setup?

You will need to migrate to RAID5. You can expand this way, but a new drive will need to be same capacity as existing drives. If you chose TRAID at the strat this would allow drive size mixing - with new drives allowed to be bigger.