Incompatible Units Problem

I am trying to use quantities with physical units to calculate my result, but I encountered the "Incompatible units" problem. I don't know what is going on. Here is my code, could I have some second-opinions?

Convert[λ^2 Ins/(πωℏ) /. ω -> (     2 π c)/λ /. ℏ -> h/(2 π) /. {Ins ->     51*10^-3 Watt/Centimeter^2, c -> SpeedOfLight,    h -> PlanckConstant, λ -> 369*10^-9 Meter}, Hertz]