More than 72 hours not get response previous questions How do I open PhPmMyadmin, So I could find my username and password of wordpress website

This is not an AWS question - but rather a WordPress one - so you would likely have more success asking this question on the WordPress forums. That said - a Google search reveals a few answers such as:

• https://my4.bluehost.com/hosting/help/wordpress-password
• https://www.wpbeginner.com/beginners-guide/how-to-reset-a-wordpress-password-from-phpmyadmin/

Those likely contain something useful to help you reset your Admin password and regain access to your CMS.

Perhaps you could try connecting to your Wordpress instance via SSH. In Lightsail console, when you visit an instance, you can find Connect using SSH button.

Once you are logged into the instance, you could try steps described in the password resetting manual's Through WP CLI section.