Get attachment meta (I need attachment ID, unsure how to find it)

“Attachments” aren’t meta data. That is why you can’t retrieve them with get_post_meta(). “Attachments” are a post type that is attached to the parent post. You need to pull the attachment posts that have you post set as parent, and then use those IDs to get the attachment meta.

$args = array(
    'post_parent' => $post->ID,
    'post_type'   => 'attachment', 
    'numberposts' => -1 
);
$children = get_children($args);

foreach ($children as $c) {
  $att = wp_get_attachment_metadata( $c->ID, $unfiltered );
  var_dump($att);
}