Hello Larry and Welcome to the Forum:
Go outside and see if anything is running in the outdoor unit. There should be a noisy motor sound from down inside it (that's the compressor) and a fan running at the top. If there is nothing going on there its time to check the breakers/fuses; there should be a local disconnect at the unit, make sure it is on and doesn't have blown fuses in it. The best way to check the cartridge fuses that are sometimes found there is to remove them and use an ohmmeter between the ends of each one.