MR1100 Port redirection (External port and Internal port)

Hi, I need to open and redirect a port on the MR1100 router. I can go to port forwarding to open the port but I cannot see an option to redirect the port. Often on other routers there is an option to redirect or you have an external port and internal port option for the rule. The SIM card I am using has a static IP address so opening ports is fine for this setup.