y wrote:how do i convert db to watt/cm^2?
Remember first that db is a measurement of the differential in power, where watt/cm² is a measurement of power.
That said, you can use:
-db = 10Log(So/Sr)
where Sr = 10^-16 watts/cm²
So, given an observed power of 10^-6 watt/cm² you'd have:
db = 10Log(10^-6/10^-16)=100 db