Civi Event Participant Status ID
An easy way to know it is goin to Admin -> CiviEvent -> Participant Status

You will see all the Participant Status. Put the mouse over the "Edit" but dont click it. And you will see the url you will be redirected if you click it. This utl is like: "http://dmaster.demo.civicrm.org/civicrm/admin/participant_status?action=update&amp;id=2&amp;reset=1"

The id you are looking for is the id variable, which in the case I show you above is 2. (id=2)

I hope this is what you need!

EDIT: No need for the link. Just int the page of Participant Status you can see it in the column:  "Name (Status ID)"