You need to work out the balanced equation for the reaction between permaganate and iron, this will then give you the mole ratio. use the mole ratio to find the number of moles of iron in the conical flask.
Then multiply this up to the size of the volumetric flask (eg if you used 25cm3 samples in the conical flask, then the no of moles in the volumetric flask would be 10x more).
Then use mass = moles x atomic mass to find the mass of iron
and divide by the mass of the hydrated crystals and x100 to get percentage
I'm pretty sure that's the method, but I'm not 100% clear on some of your steps above. I hope that helps.