In WordPress there will be a default wp-config.php file and I think this has been missing from your package. Please Check if it is there, else create a new one with file name wp-config.php and Place the following code in it with appropriate Database Credentials.
<?php
// ** MySQL settings ** //
define('DB_NAME', 'DATABASE-NAME'); // The name of the database
define('DB_USER', 'DATABASE-USERNAME'); // Your MySQL username
define('DB_PASSWORD', 'DATABASE-PASSWORD'); // ...and password
define('DB_HOST', 'localhost');
define('DB_CHARSET', 'utf8');
define('DB_COLLATE', '');
// You can have multiple installations in one database if you give each a unique prefix
$table_prefix = 'wp_'; // Only numbers, letters, and underscores please!
// Change this to localize WordPress. A corresponding MO file for the
// chosen language must be installed to wp-content/languages.
// For example, install de.mo to wp-content/languages and set WPLANG to 'de'
// to enable German language support.
define ('WPLANG', '');
/* That's all, stop editing! Happy blogging. */
define('ABSPATH', dirname(__FILE__)."https://wordpress.stackexchange.com/");
require_once(ABSPATH.'wp-settings.php');
?>