Thank you for you hel and tips...
I succesfully retreived data;
First, when I put old HDDs in new Snap, I could not see Snap on network... Then, I reseted to factory dafaults, and Snap appeared in Assist application.
After that I was not able to see HDD content and that worried me... SnapOS had older version of software (3.1.626) and I had prepared new 4.0.860, but was affraid to run because I didn't know if data structure is different between versions 3 and 4. As you wrote me, it is not, so I updated to v4, and then I was able to see one mirror disk. The other one is actually empty and I can see 128 GBs, I think I maybe formatted it or something when I was trying to run it on older SW version...
Nevertheless one mirror was enough and now I am backing it up on my PC and "normal" NTFS partition disk (just in case
) . After that I will try to rebuild RAID1 and continue tu use Snap in my home network.
Ehanks again for your help...