XCP and Proxmox typically use different disk image formats. The actual format Proxmox uses even depends on how it was installed: if you use ZFS (which I highly, highly recommend), Proxmox will use zvols to back VMs. As a result, you generally can't bring storage over directly.
When you migrate from one VM to another, the hostname in the OS must remain the same. The IP can change, though if you use a different IP, you will probably need to reissue a bunch of licenses.
The easiest way to go is to:
- Check the jumbo on the old VM (cpinfo -y fw1)
- Use 'migrate export' on the old VM to export the config
- Copy the export file to some third system (such as your workstation). Keep in mind, this file is very sensitive: it contains all of your rules and objects, as well as the cryptographic keys needed to manage the firewalls.
- Shut down the old VM
- Install the same release in the new VM (e.g, R81.10)
- Go through config_system (or use the first-time wizard)
- Install the jumbo you identified in step 1 on the new VM
- Copy the export file to the new VM
- Use 'migrate import' on the new VM to import the export file
- Reboot to let everything come up clean
I would also recommend upgrading to R81.20, but that makes this swap a bit more complicated. You would need to use 'migrate_server' instead of 'migrate export'.