If you've forgotten your password to your Standard Notes account, your only option is to delete the account and start all over.
Note: Deleting your account will permanently delete any associated notes, tags, and other data. If you're already signed in to Standard Notes on one of your devices, be sure to export your data before proceeding.
Extended users: Your notes account is separate from your Extended account. Deleting your notes account will not affect your Extended account or subscription. Simply re-add your existing Extended Code after you perform the deletion process.