User the forum search feature, magnifying glass icon upper right, and search for recover data or something similar. There are many past discussions on attempting to recover data from a My Cloud drive.
https://community.wd.com/search?q=recover%20data%20category%3A105
The My Cloud hard drive is formatted to EXT3/EXT4 which Windows WILL NOT read unless you use a third party driver, or boot that computer into Linux using a Linux Boot Disc/USB flash drive. The following post has some further information:
I take it you did not have a Safepoint/Backup of the data on the My Cloud to an external USB hard drive attached to the My Cloud USB port?
