Wavelength and frequency of any spectral radiation (radio waves,infrared thermal radiation, X-ray, visible light) are always interrelated by the speed of light, which is a fundamental constant. An example with the rounded value for the light speed:
What is the wavelength of an FM radio transmission at 100 Megahertz?
300000000 m/s divided by 100000000 Hz gives 3 m
The answer is 3 metres.
The other way round: A wavelength of 600 nm would result in 300000000 m/s divided by 0.0000006 m gives 500 Teraherz (500 times 10 to the power of 12).