When we use custom unique name for our facebook page, the facebook page id is not shown in the url.
However, there are some cases in which you might want to find facebook page id to get the script to work, e.g some plugins and button creators (although most of them now work perfect with out facebook page id and with page unique name too)
Anyway, whatever might be the reason for you, follow this tutorial to get your facebook page id without using any tools:
How to find facebook page id
This method involves getting current facebook page id by editing it.
Simply goto the facebook page whose id you want to know.
While on that page click “Edit Page” button on top right and it will take you to the page edit panel.
On this settings page, look at the url of this page, it will be like:
https://www.facebook.com/pages/edit/?id=110253005674171
So the part after “id=” is your facebook page id.
This is the simplest way to find your facebook page id without using any external tool or method.