how to change the port in a BBB


I have an internet connection and I need to share that service among 3 BBBs that are operating on the same site.

At any time, I will need to review (or change) remotely the configuration of each one. To do this, the ISP will assign a public IP to your router. I will connect the 3 BBB to a switch to share the internet service and configure the router with Network address translation (NAT), that is, to each BBB I will assign a different IP address and port. That way when I’m anywhere, from the browser (Google chrome or firefox) of my lap top, I’ll write the public IP and the port assigned to each BBB to be able to access each device.
I know how to assign a static IP to each BBB, but not how to change the default port (3000). Is it possible to program different ports to each BBB?