In the Owner’s Manual or other documents that came with the car, or perhaps on a sticker inside the glove compartment, there should be a code number that you can enter in order to reactivate the audio system.
If you can’t find the code number in either of those locations, then a trip to the Honda dealer’s service department should yield the correct number for you.
If none of these suggestions work for you, then I would suggest that you phone the Honda customer service folks at the toll-free number listed in your Owner’s Manual.