DS1515+ - Reuse two hard drives of previous DS - HowTo?

Hi folks,

Let me introduce myself briefly: I’m a fairly long time user of synology diskstations, went through various types, 2-bay, 5-bay, 8-bay. I’m reasonably familiar with Linux, not afraid of the cli, a daily macOS user and also an old time windows user that if need be to use windows needs to frequently lookup where to find something in windows…

My Question:
I have a DS1515+ with two 8TB hd’s in and this diskstation recently failed. My first reaction was to replace the power supply, but that did not solve my issue. I then read about the celeron issue and proposed fixes with adding a resistor + a transistor if not mistaken, but I did not want to go that path (maybe later on).

So what I did is buy another DS1515+.
Now I had hoped / expected that I just had to plug in the two harddrives and that they then would be recognized, but they aren’t, they are marked as “Not Initialized”

What can I do to reuse my two disks in the new Diskstation?
Is there any tutorial out here that covers this scenario?

Thanks for helping out!