Hi khotasmommy,
We understand you're having issues installing an application. We're happy to help.
To start, it sounds like the app you're trying to install is not compatible with the software version on your iPod. We'd recommend checking the system requirements for that app to see if it should work with your device. Go in to the App Store and pull up the Amazon Music app, then scroll down the page until you get to the Information section, then look at Compatibility.
If the application requires a newer software version than iOS 9, it will not work with your device. Due to the age of this iPod model, it can not run newer software versions. You would need a 7th gen iPod Touch to run the current iOS 14 software. An iPod touch 6th generation can use iOS 12, as the highest iOS version.
We hope this helps. Take care!