I think the best solution would be to buy the exact same My Cloud Home Duo. However, it could of course work if the WD My Clout EX2 Ultra simply recognises the disks and can use them. However, it could well not work either. The My Cloud Home Duo hardware uses a Realtek RTD1296 CPU with four 1.4 GHz Cortex-A53 cores and a total of 1 GByte DDR4 RAM.

However, the WD My Cloud EX2 Ultra has a completely different Armada 385 (SoC - 1.33GHz) Dual Core CPU. I know from other manufacturers that a direct transfer from one hardware to another is only supported if the CPUs are more or less identical. I think the best thing to do is to buy another My Cloud Home Duo and try to get the data back.

What I can highly recommend is a backup concept that supports the 3-2-1 rule. Three copies on two devices and one copy in another location.

A lot of people think oh I have RAID, it's all good, but RAID is not a backup. It's hardware failure protection. The best solution would really be to keep three copies of the data, also a consideration would be to switch to another NAS provider, QNAP devices are cheaper but also more complicated, Synology devices are a bit more expensive but also easier to use. With WD you have good hard drives, but usually the support at WD is not comparable with Synology or QNAP. If the data can also be copied back from another medium (not only available on the Duo disks), then I would suggest the following: Buy a Synology DS420+ or DS418, put the two disks from the Duo into the Synology NAS (4 drive bays because it is cheaper to expand) and then copy the data from the other medium to the Synology NAS and then dispose of the Duo enclosure. Good luck saving the data.