(post moved to correct forum)
See the correct subforum for your device where users more familiar with that device may be able to assist. This subforum (OS3 My Cloud) discusses a different My Cloud device, the OS3 single bay My Cloud:
OS5 My Cloud Pro Series
You may end up having to setup a VPN connection to your local network that the My Cloud resides on in order to access it remotely via drive mapping. There are plenty of DIY guides out there on how to setup VPN on the local network for remote access.
You have posted in the wrong sub-forum. My first generation OS3 WDMYCLOUD is used on my home network now.
You should post in the sub-forum for the PR2100 OS3 if that is what you have.
Latest My Cloud OS 3 Personal & Network Attached Storage/My Cloud Pro Series topics - WD Community