Hi,
Time Machine is not a reliable backup application for Virtual Machines (the main reason I developed a backup program, see my signature).
OTOH if your superduper clone also clones the hard disk that has your virtual machines you at least have a proper copy of the virtual machines in case of need.
For an easy backup of your virtual machine, shut down the VM, then make a copy of the whole bundle to an external disk.
Yes you can then drag THAT folder back to your mac and start the VM using Fusion.
Note that if you install High Sierra from scratch that you need Fusion 10 and also note that for Fusion 10 there are additional Fusion 10 system requirements over Fusion 8.
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Wil