presuming you have enabled SSH then thats not going to work as you have to login as admin now, same password as root though.
you can do a
sudo -i once logged in if you need actual root user access
im presuming you still have the old nas up so it might be simpler to do this if you dont want to muck around with SSH
- on the old nas start file station
- copy the latest backup zip from that AppData location to its
- you should be able to see it from your own workstation now so copy it to there
- copy it from your workstation to the
/data volume on the new nas
- see if sonarr restore can see it in that location otherwise use file station (on the new nas) to move it under the backup folder under that AppData location so it can see it.
once its restored you should be back to normal
long term you may want to look at using docker containers for sonarr, radarr, and sab, as it makes it incredibly easy to upgrade, move around, and get at any of their files, if you have a need to, and as they are isolated from DSM you can upgrade it and/or them without any impact on each other.