Go to your post office with your money order receipt and they will run
a trace on it. Ask them what your next step should be- you do not need
to hire any one- the person that cashed the money order has broken a
federal law and will have to suffer the consequences of their actions.
All that you need to do is file a complaint with the proper authorities.
If Western Union: Contact Western union and they will assist you in recovering the stolen funds.