Dead ReadyNAS Ultra2, how to retrieve files?

mdgm wrote:

You purchased the Ultra over 3 years ago? I find that hard to believe considering it came out less than 3 years ago. The Ultra 2 has a 3 year warranty. Easiest solution would be to migrate to another Ultra, hopefully a replacement under warranty. The partitions on the disks should be visible in Linux. If you were running 4.2.16 or later you'd need to use tools for GPT e.g. sgdisk (I think). You could use the print option to print the partition table. It's easy enough to use mdadm to start the RAID, run a vgscan, make the volume group available using vgchange and mount the volume. Oh and the Ultra uses EXT4.

I used 4.2.19 I believe. Not the very latest but one before that.
Linux (Knoppix) and Windows with the EXT add-on sees the partitions but not what's in it.
I know a tiny bit about Linux but what you are refering to above is meaningless to me without some more explanation.

How do I "start" the RAID? hook both drives to a SATA port in the PC and run "mdadm"? Is that GUI or CLI?

I appreciate your advise !