>Edit system files or install plugin
>Text editor or plugin
Plugin: Change DB Prefix
This plugin is mainly useful if you have not changed the database default prefix(wp_) at installation time and want to change afterwards so its possible by this plugin.
Plugin: WP Security Scan
Install the WP Security Scan then go to Security > Database and follow the instructions.
Note: If it will not be used for anything else remove the plugin you used after you changed the prefix and tested that it works.
If you prefer not to use a plugin you can manually change using one of the many guides on the internet.