Here you haven't specified that work function of metal is in joule or ev. So to solve it we are giving you the direction:

Calculate the energy of photon **E = ****hc****/λ **

where h (planks constant) = 6.63 x 10^{-34}

c = 3x 10^{8} m/s

λ = wavelength in metre of photon = 26.52 x 10^{-9} m

Now divide the work function (in joule) by the energy of photon you will get the no. of photon.