You will need a storage that will be your 'USB stick' . For example you can attach NFS-based storage domain, migrate the disks of the VM to that storage.
Then power off that VM, set the storage to maintenance and then detach it from first oVirt engine.
Then you attach and activate that NFS storage in your new  oVirt engine. After Activation, there will be an 'Import VMs/templates' tab . Click on it and import the VM in a cluster.
Last step is to migrate your VM's disks from that NFS to their permanent storage.

Best Regards,
Strahil Nikolov