How to calculate light intensity?

[R Sarwar]

I am calculating the light intensity of Mercury.
I was given the average distance from the Sun in AU's which is 0.39.
Using the formula (1/(d^2)), I solved for the light intensity relative to Earth which I found to be 6.57.
I need to find the light intensity in (w/(m^2))

 

[mfb]

You will need some additional input, like the intensity at 1 AU ("solar constant"), or the total power of light emitted by the sun, or something similar.