You can have several vCenters connected to Veeam ONE.
As I understood your request, you wanted to migrate performance data of one vCenter to another vCenter.
When you delete the object from Veeam ONE(VC, host, VM) all data is removed as well. If you migrate all VMs to the new vCenter Server, it will change their unique identifier (moref ID) and make Veeam ONE treat these VMs as new ones. In other words, it will not be possible to match historical performance data to the new VM instances anymore. I would recommend just keeping this database as a stand-by database for historical performance analyses.