So, I take it that you cloned the VM. To an external hard drive? If yes:
- Go to the VirtualBox Manager. Right-click on the original VM with the snapshots. Select "Remove", "Delete all files". This will delete all the VM related files and free a large amount of hard disk space.
- If you want to move the clone to your internal drive, select the clone, right-click and select "Remove", "Remove only". That will unregister the VM, but keep the files in your external HD.
- Move the directory where the clone VM is ("/Volumes/MY PASSPORT (Mac)/Win10/windows 10 Clone/" ? ) to your "/Users/<username>/VirtualBox VMs/". Open that directory and double click on the VBOX file. This will re-register the VM with VirtualBox.