i want to understand the impacts and prerequites to migrate a legacy vsphere VM to an vRA/vRo automated private cloud.
assuming the current VM is not a supported template in my private cloud, what i need to do to ensure i can migrate the legacy vsphere VM and be able to orchestrate the VM once migrated?
While I don't fully understand your exact goal (what is the legacy vsphere and how does that differ from your private cloud? and what do you mean with "current VM is not a supported template"?), the keyword here is "onboarding".
Onboarding is a process to "import" existing VM's into vRA after which you can manage the VM's with vRA/vRO.