It's not on the rear door handle of this truck. I bought it used and the handle may be after market or if it was on paper it may have eroded, but there is no number now.

Try this. turn the radio on and make sure you see "code" on the display. Turn radio off. Hold down preset numbers 1 and 6 and turn on radio without letting go of buttons. You will see the letter U with 4 digits then it will switch to the letter L with another 4 digits. Write down these digits starting with the first set.(ignore the U and L).This is your serial number. Go to a dealership, give them the serial number and ask them if they can look up the radio code for you.(5 digit number). More than likely they won't charge you as long as you ask nicely and show proof of vehicle ownership.Then just enter the code in the radio using preset numbers. They usually charge if they have to manually look up the serial number for you as well as the radio code and type it in for you.