Have you tried using one of the My Cloud apps/software or the MyCloud.com web portal to generate an email link? That may give you the public URL. Chances are however that it won’t work. Generally it is not really possible to access the My Cloud remotely without using one of the My Cloud apps/software or the MyCloud.com portal or using the insecure FTP or using an email/web link generated through one of the previously mentioned remote access methods (non FTP).
Do a subforum search for SSH and you’ll find a discussion or two where people tried to access their My Cloud remotely using SSH.
WD removed the ability to remote map the My Cloud last year. If one has an older v4.x version My Cloud they can regain the remote mapping feature by using the unofficial CloudDAVMod app.
https://community.wd.com/t/app-clouddavmod-various-versions-for-firmware-v4-09-2016/161543
