Plesk has inbuild phpmyadmin which you can use to acccess your database. To open phpmyadmin in plesk please follow the following steps:-

1) Login to Plesk control panel.

2) Click the "Domains" shortcut in the navigation panel.

3) Click the required domain name in the list.

4) Click on database (under application and services group).

5) Click on the database name for whome you require phpmyadmin.

6) Click the Webadmin icon in the Tools group. An interface to phpMyAdmin database

management tool will open in a separate browser window.