Cannot Import existing drives

[Alan of Amersham]

Hi Everyone, I was running freenas 9.10 and then updated to Truenas. I mistakenly tried to boot from the previous freenas and everything went wrong - could not boot into anything. So I have tried reinstalling both freenas 11.3 and latest truenas. Finally managed each but if I go to import an existing pool the only one that shows (I assume it is on a system ROM) seems to have a list of my various (correct) upgrades ending in a 4GB file freenas 9.10 boot file. This 'pool' is called freenas-boot and I can import it. But my 4 x 3.6TB disks, which do appear on the disk list simply do not appear as a pool. I think they were a RAIDZ2 array, do I need to add something so it looks for this?? Any other ideas. I am loathe to destroy the disk data by starting afresh!

I note that the freenas-boot pool does state degraded and has a triangle with exclamation mark.

I tried plugging in an old backup and used import existing existing. It did find that but again notes degraded. However it appears to list the folders and I made a samba share so can access these. But this is an oldish backup and will not have all the data that was on my 3.6TB drives, (just some key data such as photos). So my query is still - how might I access the full pool on the 3.6TB drives? I did remove the drives at one stage but believe I put them back in the same slots - would this make any difference if I did not??