I want to check my passports number

For what?

Smoothy makes a valid question. Generally passports are issued by the dept of state of your country. You would contact them.

P.S. I moved your question from Introductions. That forum is clearly marked as a place to introduce yourself to the community, not for asking questions.

One does not "check their own passport" there is nothing to check it for. It is issued and valid unless the government takes it away though legal action.

The visa's or resident permits in it, from various nations will also be different, and not checked by the passport number.

I can think of no reason to "check" a passport