Ok, there are two way of migrating VM replica files and depending on the variant chosen there are two procedures to follow in order to continue using existing VM replica files in the replication job.
Migration with vSphere Client. If you use cold migration to change destination datastore/host of the VM replica, all you have to do next is update replication job destination using Veeam backup console. Once you do this, your job will continue running normally.
Manual migration (copying VM files manually). Now this is where it gets tricky. If you choose to go this way, then you will have to re-register VM replica in the VI. This can be done by double-clicking on VM VMX file via vSphere Client. Be aware that this operation will change VM unique ID (moref), and you will have to not only change destination target for the replication job, but also perform VM replica mapping, as this VM will be treated as a new one due to VM ID change. There is also one thing to keep in mind in this scenario - after replica mapping all existing snapshots (restore points) will be removed.
Obviously, the first option is the easiest and the recommended way to change destination target of your VM replicas. If you still have this option, please use vSphere Client to migrate your VM replica.
Hope this helps!