For everyone’s reference, I leave the links here on this blog.
This tool helps you easily find your Facebook numeric personal ID for fb:admins social plugins and more!
For integrations of certain Facebook social plugins, like the “Like” button and “Like box”, and others, Facebook requires that you know your Facebook numeric user ID.
Unfortunately, they make this very difficult to find, especially if you have a so-called “vanity” personalized profile URL.
If you can’t find your Facebook ID, or don’t know what it is and need it, just enter your full Facebook profile URL in the above form, and findmyfbid can scrape the ID from the code of your personal profile page.
Source: Find My Facebook ID