smush pro

I got this error message when trying to upgrade to pro

Fatal error: Cannot redeclare get_plugin_dir() (previously declared in /home/content/a2pnexwpnas01_data01/99/3447699/html/wp-content/plugins/wp-smushit/wp-smush.php:118) in /home/content/a2pnexwpnas01_data01/99/3447699/html/wp-content/plugins/wp-smush-pro/wp-smush.php on line 116