I need the radio code for our 2001 Mercedes Truck ML320, took the battery out and radio sends enter code to unlock

Check your owner's manual - otherwise you will have to get the radio code from Mercedes. They are unique to each vehicle.

Some dealers will give you the code some only need the model and/or serial # on the radio some only need the vin # it all depends on manufacturer,make, and model some dealers require proof of ownership with valid I.D.