The Move-VM cmdlet uses vMotion. So if you have powered off the vCenter server, then you can not use the Move-VM cmdlet to move it.
You could unregister the vCenter server from the old host and register it again on the new host.
Something like:
Connect-VIserver oldHostRemove-VM -VM vCenter -Confirm:$false
Disconnect-VIserver oldHost -Confirm:$false
Connect-VIserver newHost
cd vmstores:\newHost@443\Datacenter\Storage1\vCenter\
$vmxFile = Get-Item vCenter.vmx
$vmhost = Get-VMHost -Name newHostNew-VM -VMHost $vmhost -VMFilePath $vmxFile.DatastoreFullPath
Disconnect-VIserver newHost -Confirm:$false