I think you can convert your templates into an virtual machine and follow the Migration article:
You have to prepaire your template first. Install for example the VirtIO Drivers.
I don't think it would be direct template migration even from ESXi cluster (Non Nutanix) to ESXi cluster (Nutanix)
It should be convert to VM first CMIIW
If using AHV then you need to install NGT first before migrate it to Nutanix (AHV)
Let us know if any of the replies below have helped.
To also help other community members, if you find an answer that helps, consider clicking the 'Accept as Solution' - This will help others find an answer quicker.