How do I change my router 2.4from 5 ghz

It would help to know the reason for the question.  While over 95% of typical "internet gizmos" are entirely compatible with Netgear Orbi routers, there are a few devices which have poorly written smartphone apps and be a struggle to get set up on the network.  Once set up, people have no further issues.  In those cases, there is usually a specific error message or indication in the app.

For many years, it was "common knowledge" (i.e. folklore myth) that devices require a WiFi system to be "2.4G only" in order to connect devices.  Those days are long over.

More detail would help discover ways to help.