Adam, you want to upgrade your on-prem NG to 11.26.3.6, as the VHM export capability was only added then (as it is required for the upgrade process to 12.8.0.3).
See also the Release Notes, http://docs.aerohive.com/330000/docs/help/english/ng/Content/reference/virtual-appliance-release-notes.htm
Should be able to. If you click on the silhouette, go to Global Settings, click VHM Management, then Export VHM, then go to the same place in the on premises version and click Import VHM, that should do it.
