Add this code to your child theme’s functions.php file:

//For cm unit
add_filter( 'wpcargo_package_divisor_cm', 'custom_wpcargo_package_divisor_cm' );
function custom_wpcargo_package_divisor_cm(){
	$divisor = 6000;
	return $divisor;
}
//For other units
add_filter( 'wpcargo_package_divisor_inc', 'custom_wpcargo_package_divisor_inc' );
function custom_wpcargo_package_divisor_inc(){
	$divisor = 6000;
	return $divisor;
}