The speed of electromagnetic waves is a constant. It's equal to 3.0 x 10^8 m/s in a vacuum. since 1 meter is 10^9 nanometers, this would equal 3.0 x 10^17 nanometers per second.
The relationship between speed, wavelength and frequency of waves is:
speed = frquency x wavelength
Since the speed of electromagnetic waves in a vacuum doesn't vary it would be more likely that you're being asked to calculate either the frequency or the wavelength. Rearranging the equation for speed, you get:
wavelength = speed/frquency
frequency = speed/wavelength
Light moves more slowly through substances than it does in a vacuum. In order to calculate the speed of light in a substance you need the index of refraction for the substance, which is the ratio og the speed of light in a vacuum to the speed of light in the substance.