Since WordPress is an open-source CMS (Content Management System), the WordPress community gives both new and experienced users a lot of FREE documentation. Here is a helpful WordPress reference piece about how to find the WordPress Page ID in the backend admin area.
Locating the page with the ID already known:
You can learn that to find the WordPress page ID for any WordPress page you are working on, you only need to type “http://www.yoursite.com/?page_id=” into your browser’s address bar. Replace “www.yoursite.com” with your site’s URL and “?page_id=” with the WordPress page ID you want to find out. Do this right before the URL of the WordPress page you are on.
For example, if you were working on WordPress Page ID #1000 in the WordPress backend, you would type http://www.yoursite.com/?page_id=1000 into the address bar of your computer. With the WordPress page query parameter, the WordPress backend will immediately look for the WordPress page.
So, if a WordPress custom post type were specified in the WordPress Page URL, for example, and instead of http://www.yoursite.com/?page_id=1000, it was typed into the browser address bar as http://www.yoursite.com/products/my-product/?page_id=1000, the WordPress backend would think you wanted to learn more about WordPress Page ID # 1000 within WordPress Post Type: Products. I mean to add “?page_id=” to the end of the URL of any WordPress page to find its WordPress page ID.
Finding out the Page ID where it is not known:
Once you’re in the admin area, go to “Pages” > “All Pages” and find the one whose ID you want.
Remaining on this page, hover over the page in question, and you will see a URL in the left corner.
You are looking for a number. It is the PAGE ID for that given page.
In the example below, the PAGE ID is 81445.