How to copy my old MBLD disk to a new MBLD system

I tookout the derives from my MBLD 4TB system ( that stopped working). I received a new replacement -

now I am trying to find out if I can just replace the new drive-B with  the old drive-B  and under RAID-1 configuration

will the new MBLD will start copying the files to Drive-A.  —I was told by WDC customer support that I can  …

It does not work - The dribve boot up  and than immediately  goes to RED LED.

In the WDC menu  I get an error that System failed - drive-B.

what is the proper way to move the data from the old drive(s)  { I was using raid-1 before } to the replacement system.

No, that won’t work.

You’ll most likely need to completely remove ALL PARTITIONS on Drive A before you do that, otherwise the Duo won’t know which RAID member is the correct one.