Reach is the easiest figure and says the least. The question is what happened next.
Part of the effect cannot be attributed. Someone sees a story, buys three weeks later after searching for your brand name, and that purchase is credited to Google. If you steer on discount codes alone, you will structurally underestimate the channel.
Look at what happens to your total revenue and your brand searches in the weeks around the posts, compared with a period without them. It is cruder than a dashboard, but it separates cause and effect better than any attribution model.
A question or project on this topic?