Question

Solar radiation falls on Earth’s surface at a
rate of 1900 W/m^2
.
Assuming that the radiation has an average
wavelength of 560 nm, how many photons per
square meter per second fall on the surfaces?
The speed of light is 3 × 10^8 m/s and Planck’s
constant is 6.62607 × 10^−34
J · s.
Answer in units of photon/(m^2· s)

Okay so using ΔE = hf with h as planck's constant and f asfrequency, I plugged in f = c/λ with c = speed of light and λ beingthe wavelength.
Came out with ΔE = hc/λ, some constant J per photon

I converted Watts into Joules per second
so I ended up with (1900 J/m^2·s)/(ΔE J/photon), the units cancelto be photon per m^2 per second but the constant 1900/ΔE seems tobe incorrect. Am I using the right method?