Everyone who signs up here has an id number. You can see it in your personal page. I'm 47108. You're 89567. The smaller the number, the higher your seniority. The number 1 has been deleted, so the eldest members of the forum are omnscient0 who is id=2 (and has been inactive for five years) and Casusby who is id=3 (and is the most senior active member, admin and moderator).
where can you find your personal page? I've only ever seen manage/edit your profile
Like the above poster said, the op probably meant the page where your personal posts (all the posts authored by you) are listed. To reach it, the easiest way is to click on the number under your avatar pic that reads xxx posts:

Then you reach the page where all the posts under your name are listed together, and if you look at the http address of the page...

You'll see that the address ends with id=29405 which is Meursault's id number as a forum member.
You can check the listed messages of any poster, not just yours, by clicking on the "number of posts" line under the avatar pic. And at the same time find their id number.