Can anyone help with how-to create subfolders

I used to be able to do this in my previous mycloud mirror but can’t seem to get it to work on my PR2100. I am accessing the drive in Finder on my Mac, I have already created a share and I have access permissions… I am trying to copy and paste folders (with photos) from the mycloud mirror to the share folder on the PR2100 but the system will not allow me. I also cannot seem to find where I can go into the share in the PR2100 and manually create the subfolders. Any help would be appreciated, thank you in advance!