If you can't remember the passcode for your Kindle, you'll need to reset your device.
Important: Resetting your Kindle will remove your personal information (including your lock screen passcode), Amazon account information, and downloaded content. Any content you purchased from Amazon is automatically saved to the Cloud. You can download that content when you register your Kindle to your account again.
To use your Kindle again, you'll need to connect to a wireless network and register your Kindle.