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.
Use a magnet to remove the iron filings first. Then pour boiling water into the sand/salt mixture and stir it until the salt is dissolved. Filter off the sand and set it aside, then boil the salt water until the water evaporates or leave it in an evaporating basin. You now have three separate piles of iron, sand and salt, although I doubt they'd be really pure.
In the future, you can get a faster answer by searching questions that are already closed. (A search for "sand, salt, iron" brings up other chemistry students who have also asked this question.) Have fun!