Here is the tips for getting page id in wordpress. First of all I will show page id in admin area.

Go to the pages and clcik on that, then you can see all pages list. Look the below screenhsot.

After then click on the desired page and you can see the page id on the address bar as I have marked. attached screenshot.

If you want to check page id on the front side then you should use the code. Use the blow wordpress function . It will give you the page id on the pages
get_the_ID();

More detail you can get here

If you want to show page id only for specific page then you can use the below code
<?php if(get_the_ID() == ‘475’) {?>
I am your page
<?php } ?>