You can find your Facebook Post ID - needed for the Comment to Messenger feature - in the direct URL to your Facebook post
In order to use our Comment to Messenger feature, which allows you to drive people to your Messenger channel by commenting on a Facebook post, you will need to find the Facebook post’s ‘Post ID’. This Post ID is a string of numbers at the end of a Facebook post’s URL.
The easiest way to find your Facebook post’s direct URL is to go to the post itself in your Facebook Business Page newsfeed, and right-click on the date/timestamp on the post and open it in a new tab to go to the direct link of the post.
Now that we're there we can look at the address bar of your browser and find the id from the URL.
Post with just text:
The story_fbid= is the post ID we want to copy.
Post with an image:
The final set of numbers is the post ID we want to copy.
Post with a video:
Please contact us (email@example.com) for support on your video post. We can get the post ID for you.