good place to start is here: https://clouddocs.f5.com/api/irules/
selecting pools is explained here: https://devcentral.f5.com/s/articles/irules-101-05-selecting-pools-pool-members-and-nodes
and example to look for destination port can be found here: https://devcentral.f5.com/s/question/0D51T00006i7R4A/irule-to-send-to-server-by-destination-port
help yourself and post what you think would be the correct iRule (even better also test it on your BIG-IP), someone will certainly help you out on any missing details then.
