Place an iron pill in a beaker and add 20 ml of 1.0M H2S04, then transfer into a 250 ml volumentric flask.?

If the concentration of 1.00 ml of this solution is 1.2875X10-5 M what was the mg of iron(II) in the original pill? Basically I am confused about how to convert to mg from ml. I know water's density is 1.000 but I added H2SO4 and Iron so can i still use that number?