Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
If you don't remember the passcode/password, you have to reset your Kindle to factory settings. Unfortunately that is your only way to access your Kindle.
Resetting will erase everything from it, but you can re-register it with the same Amazon account you used on it to redownload your books without paying again.
Enter the incorrect password ***** multiple times and it will ask you to reset it. If not, enter any of the passwords below to reset;
If that didn't work, then enter resetmykindle (without space) in the password ***** and confirm it. This will reset your Kindle.
After resetting the kindle, you can redownload all your books to it using the same account you used to purchase them.
If you don't remember the password ***** your Amazon account, then you can reset it from here --> https://www.amazon.com/gp/css/account/forgot-password/email.html
Please let me know if that didn't work, so we can continue troubleshooting.