The My Cloud creating multiple duplicate USB hard drive entries has been discussed in the past. The workaround is to eject each of the USB drives through the My Cloud Dashboard. Then access the Shares page in the My Cloud Dashboard and remove any duplicate USB Share names. Then reattach each USB drive to the My Cloud. Then rename the Share name in the Dashboard Share page back to the original USB drive name. See just a few the following discussions for more information. More can be found using the forum search feature, magnifying glass icon upper right.
https://community.wd.com/t/new-release-firmware-release-04-04-02-105-1-27-2016/148441/68
https://community.wd.com/t/mycloud-creating-numerous-aliases-for-same-drive/160161
https://community.wd.com/t/usb-drive-makes-new-name/152675
https://community.wd.com/t/dublicate-shares-after-reboot/153348
