Lost Key!

I have a 2004 Honda Rancher… TRX400FA. I bought if from a buddy, who bought it from a guy he worked with. It came with one key, and my wife has lost it! The key only had one single number on it. Is that the code needed to order a new key? Is there another way to figure out the code, cause I’m only 97% sure of the number that was on the key! Any help would be appreciated! Thanks! 🙁