I have an older fan light combo that was controlled by a switch that had a rotary dial for both light and fan. The metal switch plate was becoming hot to the touch so I decided to replace it. Inside the box are two pairs of three conductor wire. The two black wires are joined together and the two white wires are joined together. The two red wires then go into a very old NuTone switch. Ground wires from each set are also joined and go to NuTone switch.

How to a wire this to a new fan control and dimmer switch that has connections for red, white, black and ground?

Many thanks