Please help with calculation!!

I'm trying to find the mass of iron in an iron tablet using a colorimeter. Please can somebody help me!

I crushed an iron tablet, dissolved it in 20ml of 1M sulphuric acid. I then added potassium permanganate (about 4ml). I transferred this to a 250ml volumetric flask and made to the mark with water. I then took 5ml of this solution and added it to a 100ml volumetric flask and made this to the mark with distilled water. 10ml of this solution was transferred to a boiling tube and I added 10ml of ammonium thyocyanate.

I used the colorimeter, made a calibration graph and found the concentration of the iron solution was 2x10-5M.

But now I'm kind of stuck. What volume of iron do I use if I'm trying to find the number of moles in this iron solution?

Hey, this technique sure is complicated!
I would start this by using the value of 10ml (or .01 dm^3) and the concentration you've given from the graph. Once you know the number of moles in this 10ml, you can work backwards to get the no. moles in the original solution!

Does this make sense to you?

How would I work backwards to find the moles of the original solution?

I know what to do after I've found the number of moles, but this part is really confusing for me. Probably because I've been working on this project for hours and hours

Thank you so much for replying