You won't find ANY syringe that will measure in mcg, mg, g, etc. They read by volume, the volume contains your concentration. If that makes sense.
What is your concentration? How many mcg per mL? In other words, how much water (mL) did you add to how much (weight) of powder?
Then you figure out your concentration from there.
Say you added 1mL to 1mg of powder. You'd have a concentration of say 100mcg per 0.1mL or 1mg/mL. You can figure out the rest from there I hope. Assuming you mixed it as I mentioned above, you would have one tick/mark equaling 10mcg.
100 marks = 1mL. 1mg divided by 100 marks = 10mcg/mark.
Edit: Sorry if that's a little confusing. I can do the work in my head but without pen and paper it's hard to describe in words what to do. I basically taught my class how to do this crap for nursing. So much easier with the items in hand!