Q: itunes only listing 1 app on my iphone. I have 42 apps

Use your PC iTunes and download the rest under Purchased.

Read here for instructions: Download your past purchases - Apple Support

If you are referring to apps that have been saved in iTunes, then that's fine. There's no longer a need to keep copies of apps on your computer.

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With iOS 9.2 you are no longer able to move apps from a device to iTunes. Apple now uses a system called App Thinning. With it, when you download, or update, an app on a device, only the resources needed for that specific device are downloaded. This makes the download substantially smaller and quicker. But it also means that that exact version is useless to any other device, so it doesn't get moved to iTunes. If you do want it in iTunes, you have to download it from the App Store directly (or set this to be done automatically). Personally, I stopped keeping copies of apps in iTunes  - no reason to waste disk space. I can always redownload them from the store. The one exception is an old, but stil working app that's been abandoned by its developer.