This is a relatively simple question given the formula and the important constant. The constant that we will need here is the speed of sound. That is 3.00*10^8 m/s. The speed of light is equal to the wave length times the frequecny. We are given the frequency and speed of light, wavelength is then computed as follows:
wave length = speed of light / frequency = 3.00*10^8 m/s/ 10^19 s-1 = 3*10^-11 m or 0.03 nm