1mg is 3 iu of GH, but you dont need to worry about that. All you need to know is how many IUs you plan to run. GH is much more stable in its powder form. Once you reconstitute it, it become much more fragile and over time, will break down faster. You want to mix one vial at a time, using bacteriostatic water. if you mix 1ml of water, then every .10ml or "10" on your insulin pin, will be 1iu, if you are using 10iu vials. Make sure to store your GH in the fridge. 

If you need help with the reconstituting process, your best bet is to get a visual demo that you can find on youtube. I have explained it here a few times before, so if you like you can look through old answer, but still, I think the visual would be easier to understand