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 108 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.