You have posted to the My Cloud subforum. The My Cloud is a Network Attached Storage device not an external USB hard drive. See the External Drives for PC subforum if you have a WD My Book USB external hard drive: https://community.wd.com/c/wd-external-drives/external-drives-for-pc/24
Search Youtube for videos on how to “shuck” the My Book enclosure and replace the hard drive. However you will find, that many times, one can buy a new WD external hard drive cheaper than a bare hard drive. A newer hard drive will be USB 3.0 versus USB 2.0 or USB 1.0 from old external hard drives particularly those under 500GB’s.
You are trying to repair a 17 year old external hard drive that has USB 2.0. You will likely be better off unless you have a specific requirement for the features on that specific device, to buy a brand new external USB 3.0 hard drive. When connected to a USB 3.0 port on a computer/device that USB 3.0 external hard drive will typically transfer/operate significantly faster than the 17 year old external USB 2.0 enclosure. In any event see the External Drives for PC subforum where such external hard drives are discussed.
(Next day.) Well, I found that replacing the hard drive was a day dream. To extract the old one requires destroying the case. One can’t access screws without cracking and removing plastic. Boy, was that case well engineered. I’ve seen military radio equipment that would give this case a salute.
When I finally got to the hard drive, ha, I find it’s IDE! (For newer computer builders, IDE was very old technology, long replaced.) And I can’t find my IDE to USB adapter.
So Bennor, you were right. I was on a fool’s mission trying to replace the drive.