If you have a public IP, you should set up DDNS and be able to access MT300N-V2 remotely via the ddns. Then you should do port forwarding from MT300N-V2 to your NVR. In this case, you can access the NVR remotely via your ddns and port.

You need a public IP in order to do above.

But if you do not have, we will have a different solution for you. We are still developing it and you may try in 1 month.