I have about 600 custom type pages (CPT Name : pack), each of them holds about 50 to 100 image attachments,
they do not show up on the admin edit screen, how can I display them on the Admin edit screen using Metabox ? Which of the types do i have to use (file upload , file advanced , image advanced, image upload) how do I tell metabox to use the attachments ?
If you attach a media file to a post on the Media page > column Uploaded To, that means the post is set to the parent post of the media file (find in the column post_parent, table wp_posts)
This is not a post meta so it is not possible to create a custom field to assign those values to the field and display images when editing the post. You need to create a field like image_advanced and select images manually.