Hi If I understand correctly you are looking to get the data associated with a custom post type that was generated in your WordPress environment created by the theme.
This can be tricky to understand if you are not familiar with WordPress.
Typically to get any kind of data with any type of post type you can use the get_posts() function (see WordPress docs) provided by WordPress. This typically looks like this:
$args = array("post_type" => 'custom-post-type-name', "numberposts"=> '-1');
$post_query = get_posts($args);
What this does is retrieve all the posts with that post type and returns them in an array of WP_Post objects. (See WP_POST Docs)
What you can then do is iterate through that array and access the various items you may wish to use that are associated with that custom post type (assuming there are custom properties). Since custom post types are typically an extension of WP_POST you will have access to all the available properties of the WP_POST object.
What that looks like in code:
foreach($post_query as $post){
//The title of the post
echo $post->post_title;
// The content of the post
echo $post->post_content;
// If you custom post type has a custom property
echo $post->custom_property_name;
}
This is a very basic overview of custom post types and how to access them and I would recommend looking more into them by reading more material on them.
As for the code above you can simply put it into your functions.php and it should work. If you are in a development environment you could do the following to take a look at what your custom post type looks like in your functions.php file:
add_action('wp_body_open', function(){
$args = array("post_type" => 'custom-post-type-name', "numberposts"=> '-1');
$post_query = get_posts($args);
foreach($post_query as $post){
var_dump($post);
return;
}
});
As far as managing custom post types goes here are some helpful articles from websites I use on the regular to get help with WordPress related projects:
WP Beginner
Kinsta Resource
Smashing Resource
Best of luck!