You can’t know for sure whether individual people see your posts. You can get some general data from your Facebook insights page, however. This will show you page, post, and video data for the mast 28 days. This gives you key metrics for your page and the posts you have made. This will show you which posts had a particularly good (or bad) response. Post Reach shows your basic post reach stats such as impressions, engaged users, consumptions, and video views.