All download manager packages are WordPress custom post types,  so you may use get_post($ID) to retrieve regular post data. Other custom package data like download count, view count, package size are stored as post meta, so you may use get_post_meta function to retrieve any package data. For example, to retrieve download count, you need to use get_post_meta($ID, '__wpdm_download_count', true);. However, wpdm also has a function to retrieve specific package data, which is explained here:

https://www.wpdownloadmanager.com/doc/function-reference/get_package_data/

More Function References:

https://www.wpdownloadmanager.com/doc/function-reference/