Write MBR to older WDMyBook USB 2.0

Hello WD Community members,
as You can read in my headline, I wanted to ask how I can write a lost MBR back to a fully funktional WDMyBook model number wdbacg0020hch-00.
This is why I ask: I wanted to copy my data from this old model and extended the hdd from the case. So I connected it with USB 3.0 fantec adapter and thought this will be faster than USB 2.0. So in first case the HDD was not shown, so I went to the volume maintenance under W10 and builded a new MBR/GUID and set the volume letter. At this time it was not clear for me, that WDMyBook has a hardware encryption active all the time implemented in the SATA Adaptor of the WD case, so my data was not visible any more because of a new MBR and no encryption. After research I could rescue my data using easeus and the WD adaptor for encrypting.
Now I only want to ask, if somebody knows, how to write back the real MBR, with adapor from WD. I know data is saved, but at the data rescue search, a lot of old data was also found, which makes it a litte bit “much”. So if here is a person who can tell me what tool or order (maybe fdisk) I can use without destroying the encryption completely and maybe get back the “original” version of my USB 2.0 WDMyBook without “old” data, it would be great.

Thank You in advance!