To see those parts in their "natural habitat" here's a link to a picture over on the ninja250.org How-To pages:
https://faq.ninja250.org/wiki/File:Carbs.jpg
When they are installed properly you will see them at the bottom of the Airbox side of the carbs, peeking up just under the vacuum slides.
(Don't lose them and get them back in the carbs all proper when you're finished rebuilding, the bike won't run without them)