If you don't want to do a full migration, there is a different but tougher option. You could restore a C5 backup to your C8. That would bring in your automations, dashboards, driver/app code, and so on. It does not bring in the Z-wave radio database doing a local restore.
Zigbee devices would simply need to be put into pairing mode, and they would fall right back into place.
For Z-wave, you would have to rename the old DNI on all (Z-wave) devices. Then you reset and re-include the Z-wave devices. (ensure you don't create a ghost at each inclusion) From there, you do a swap device using the built-in swap app. This post has more detail as to what needs to be done if you use this method... Migrating a Z-Wave Network
I did this method when I migrated from C5 to C7, and while it was time consuming, it was worth it in my opinion so I could start over with a healthy mesh building the right way instead of haphazardly like I did the first time.
