Your Kindle Fire lock screen password ***** PIN is different from your Amazon account password.
Important: Resetting your Kindle Fire will remove all content downloaded to it. Any content you purchased from Amazon is saved to your Kindle Library in the Cloud and will remain in the Cloud. You can download that content again if you register your Kindle Fire to your account again.
To use your Kindle Fire again, you'll need to connect wirelessly and register your Kindle Fire.