Thanks @petro. When you first suggested looking at the migration guides to find my network key I searched and found this Z-Wave JS - Home Assistant (home-assistant.io). The detail about core.config_entries wasn’t explicit there so I posted the detail here. I now see the guides you have written on the forum How do I switch to Zwave JS? - Configuration / Z-Wave - Home Assistant Community (home-assistant.io) which are comprehensive (thank you for writing these!).
If you look at the integration page for Z-Wave JS it specifies the following “we currently do not provide a full-fledged, worry-free, click-a-button, migration from old to new. We’re exploring options to provide this in the future.” I guess that is what I was hoping for based on the official documentation.