I wouldn’t even try. If the DAS from the past works for you on a MAC and serves a purpose, then keep it there. Use it to hold a/the backups of important stuff like for example your digital music library. You can easily get single USB drives with 12TB and more capacity nowadays (that will also need only the power of a single drive instead of 6 drives). There is also a manual for the Nucleus:
No Thunderbolt 2 connector, just read-only support for HFS+, unclear if the RAID in that thing would be detected – if there were a way to connect it, that is.