where are apps in itunes

Apple removed app management starting with iTunes 12.7. Read the second document on various ways to do this including using an older iTunes and manually installing ones already on your computer.

Changes in the new iTunes [12.7] - https://support.apple.com/HT208075

Managing apps with iTunes 12.7 or later - https://discussions.apple.com/docs/DOC-12234

Manually manage content on your iPhone, iPad, or iPod touch using iTunes - https://support.apple.com/HT201593 - "Manually add items from your computer: If you have media on your computer that you can't redownload from the App Store or iTunes Store directly on your iOS device, such as custom ringtones or iOS apps, you can drag and drop the media from your computer to your iOS device using iTunes."

Deploy apps in a business environment with iTunes - Apple Support - https://support.apple.com/HT208079 - Downgrade to iTunes 12.6.4

http://www.apple.com/feedback/itunesapp.html