What My Cloud model’s do you have? Officially one cannot cannot backup from one 2nd gen v2.x firmware single bay My Cloud to another remote 2nd gen v2.x firmware single bay My Cloud. WD disabled the “remote server” option in the 2nd gen v2.x firmware single bay My Cloud. The My Cloud Mirror and above multibay My Cloud units support being a “remote server”. See the following WD Support document for more information:
https://support.wdc.com/knowledgebase/answer.aspx?ID=13854
Unofficially it may be possible using the unsupported GoodSync app. Note installing this app generally requires using SSH.
https://community.wd.com/t/app-goodsync-for-wd-my-cloud-backup-and-file-synchronization/173984
