OK, so dump the whole lot in a cup. Cover a magnet in cling wrap (so you dont mess your magnet) and run it through the sand to pick up the iron filings. Remove the wrap to collect the filings. Next, fill the cup with water and stir until the salt is dissolves. somehow get the sand out and dry it, but keep the water. then leave the water and it'll evaporate, leaving the salt crystals.
Ummm I would get a magnet and catch the iron fillings. Mix the salt n sand n water... mix it together n sift the sand out n boil all the water n salt should be left in the end