Order does not matter, ZFS uses UUID to identify drives. It’s a unique, serial-number-like identifier.
As long as all the drives in the pool can be ‘seen / presented to’ the CPU, it’ll import the pool just fine. So you could move connectors around on the motherboard, add a HBA, etc. it doesn’t matter. If you move stuff to a HBA, you’ll have to ensure that the HBA is presenting the moved drives to the CPU.
UUID is not the serial # of the drive. The human-readable serial number associated with each of my hard drives is printed on a separate sticker on the edge / back of each HDD (thank you, HGST, RIP), see here.
If your drives do not feature a serial # on the edge or the drives are not visible inside their hot swap bays, then I suggest using a label printer to mark them or the hot swap cover associated with each drive.