I would think that you can use the build-in OH backup utilities.
Found this thread that has some more details.
(I do run OH in a Proxmox container since the start, hence never had to do such a migration)
Edit: The good thing is that you could simply try it out. Create your Proxmox VM/LXC, get the basic debian/etc. install done, take a snapshop, install OH and restore the backup and see where you get with it. If it does not work, revert to the snapshot before.