You’ll have to configure some port-forwarding on the router.
You didn’t mention the model of netgear equipment, but from a problem description I assume it’s a small device with a web user interface for configuration. You’ll have to login into the router – follow the documentation for address, username and password. First locate its DHCP server configuration page and assign a fixed IP for the “original computer” (based on its MAC). Then locate port-forwarding page and configure the router so any incoming request to the necessary for security cameras operation ports should be forwarded to the internal IP of the “original computer”.
Agreed – some simple port forwarding is all you need. Further, you could statically assign the cameras and servers static IP addresses. This will eliminate any issues with the IP addresses changing should you lose power and the devices pull different IPs from your DHCP scope…