To be able to perform vMotion you need vCenter. I think you should be able to download vCenter from;
Without vCenter there are a couple of ways to perform a migration. If you have shared storage that is connected to both the old and the older ESXi host, you can simple unregister the VM on the older ESXi and register the VM on the bigger ESXi host. The VM's will face downtime with this way of migrating.