copying from unassigned device to array

So I've recently had a power cut that caused a few issues though I had just bought a new 8TB ironwolf to replace a couple of older 1TB drives from the dawn of time.

Typically though, this drive was DOA and the issues have taken out one of the 1TB drives.

I've bought a new 8TB WD Red that works great. I've used unbalance to migrate the old drives data to the new drive so I can get rid of them as they were starting to show smart errors.

My question is this.

The seemingly dead 1TB looks like it's working through a USB to SATA adaptor on unassigned devices and I would like to get the data from it back on my array but I'm unsure of the command to use with rsync to copy it from the old drive to the new array drive.

Obviously unbalance can't see it as it's an unassigned device.

Any help would be really appreciated.

Thanks