Both these things can not be related to each other since these are aspects of two different things.
Wavelength is the distance between two consecutive crests or troughs in a transverse wave and two consecutive compressions or rarefaction in a longitudinal wave i.e. its a property of a wave. While Focal length −The distance between the pole and the principal focus of the mirror is called the focal length (f) of the mirror i.e. its a property of a mirror itself.