There is currently no way to look up app bundle IDs in the Apple iOS App Store directly. To find the identifier, you will need to look at a file inside the app.

For Apps in the App Store

1. Search for an app in the App Store via the web - https://www.apple.com/ios/app-store/
2. Extract the unique ID in the URL
   1. For Pages: https://apps.apple.com/app/pages/id361309726
3. Open a new tab in your browser and go to https://itunes.apple.com/lookup?id=XXX
   1. Replace XXX with the unique ID found in step 2
   2. For Pages: https://itunes.apple.com/lookup?id=361309726
4. Download the file to your computer
5. Open the file downloaded and search for “bundleId”
   1. For Pages: com.apple.Pages