Conversion of units for concentration: mol/l to ppm The concentration of an aqueous solution of $\ce{Mg(SO4)2}$ is  $0.001\, \textrm{mol} \cdot \textrm{dm}^{-3}$.

Find out the concentration of solution and the concentation of $\ce{Mg^{2+}}$ ion in ppm.

How to do this? How to find moles in ppm?

If anyone could clearly describe, it would be great.
Convert mol-dm^2 to grams/volume.  A decimeter is 10 cm.  A dm^3 is then a liter.  Water has density ~1 g/cm^3.  Multiply the g(Mg)/g(water) by a million.