Utilize 1st Post Image as Featured Image

I am looking to utilize the first post image as the featured image. Going in and doing each one manually is very time consuming as there are 1200+ posts. A script was written to add images as the thumbnail under the “Latest Articles” section on the homepage, but if you look at any of the other sections or pages, anything before May 4, 2017 doesn’t show a thumbnail and doesn’t have a featured image.

Looking for any help to get this done quickly.

Utilizing the Newspaper theme

The page I need help with: [log in to see the link]