Since both of them are per liter....then all you need to do is a one step conversion of moles into grams using the molar mass...essentially you are going to multiply the mol/L by the molar mass in grams of the given substance...
1 microgram = 1 millionth of a gram or .000001 - so, just move the decimal point over to the appropriate position. As long as you don't change the value of the number, you can do what you want to it.
Use the Ideal gas Law, which is Pv=nRT.p=pressure(in atm)v=volume(in liters)n=moles(per gram)R=constant(0.0821 [(Liters x atm)/(K x mol)]t=temperature(in kelvin)find the values of each and solve for...