From the information give, I'm going to assume the wave is in a vacuum...
You use the equation: f= [tex] \frac{C}{Wavelength} [/tex] where c is the constant for speed of light ([tex]3.00 x 10^{8}[/tex]
so f= [tex] \frac{3.00x10^{8}}{6.14x10^{4}} [/tex]
f= 4.89 x [tex]10^{3}[/tex] Hz (approximately)
