debian – Using a software raid array after os failed

So I have a debian home server that has a 4 disk software RAID 5 array. My OS runs only on a normal nvme SSD. I know thats not secure, but it is a home server, so I didn’t really care when I installed it and now it is too late to change it. I was wondering what would happen to my software RAID when the OS failed (or the SSD).
How could I resync (I don’t know what the correct term for it is) the array to use it after I bought a new ssd and installed a new OS?

I found something regarding the mdadm config, but mine is empty…
Just for clarification: this is just something I thought about to be prepared when it happens (I don’t want to loose all my data)

Thanks for your answers in advance