Where is measuring device installed on iPhone 13?

Hello there!

You may find it in the application library, the last page on the right, use the search bar to find it. If you don't find it, download it through the following link.

https://apps.apple.com/us/app/measure/id1383426740

Should be an app that was already installed. If you can't find it on your Home Screen, then try searching by swiping downward on your Home Screen. Or swipe left until you get to the App Library and locate it there. Swiping down in the App Library will give you an alphabetical list of all the apps on your phone.

If it's not on your iPhone, then go to the App Store and download it.