How to determine your database prefix
From Joomla! Documentation
There are two ways to determine your database prefix. One requires access to the root of your Joomla! site while the other requires access to the Joomla! back-end.
Using the Joomla! Back-end (Super administrators only)
- Log in to the Joomla! backend.
- Go to Global Configuration by clicking the button in the control panel or via the menu (Site > Global Configuration).
- Go to the Server Tab.
- Under Database Settings, look for Database Prefix field. The value you find there is your database prefix.
Tip: Look for the yellow warning symbol
Using Configuration.php (Requires Access to the Site Root)
- Go to the document root and find the configuration.php file.
- Open the file in a text editor.
- Search for the word dbprefix.
- You'll see the line var $dbprefix = 'value'. The value you see here (for example, jos_) is your database prefix.