Most places that sell money orders will cash them.

Money orders can be purchased from a variety of places including banks, the US postal service, convenience stores, grocery markets, check cashing service outlets etc. Big names such as Walmart and Western Union sell money orders.

The Issuing Institution: The easiest money order cashing route is to go directly to the issuing institution. With the proper identification, you should have no problem cashing it.

Your Financial Institution: As a service to its customers, your bank will generally cash a money order for you as long as you have an account with funds that can cover the check in the case it is returned.

Check Cashing Services: Most check cashing services will cash a money order, but expect to pay substantial fees that may include a flat fee and a percentage of the total cash value.
Retailers: Some retailers and convenience stores may cash money orders. There will likely be a fee and you will need valid identification.