How to correctly enqueue the parent and child theme stylesheets in the creation of a child theme? [duplicate]

Check this codex page.

In the event that a child theme is being used, the parent theme directory URI will be returned.

So if you want to include your other css files you just need to all your CSS files:

add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles' );
function theme_enqueue_styles() {
    wp_enqueue_style( 'parent', get_template_directory_uri() . '/style.css' );
    wp_enqueue_style( 'custom-handler-one', get_template_directory_uri() . '/custom-css-one.css' );
    wp_enqueue_style( 'custom-handler-two', get_template_directory_uri() . '/custom-css-two.css' );
    ...
    wp_enqueue_style( 'custom-handler-n', get_template_directory_uri() . '/custom-css-n.css' );
}

Please note that some themes are coded in strange ways so this methodology may not always work. If you share the theme’s name or how the styles are included more detailed description can be provided :).