How can I tell if my apps are something I paid for, nor not? Apple iTunes.

I want to clean up my iTunes (and iPad). Over the years, I have well over 50 apps. I think 10 of them are apps I paid for. The rest are free apps.


I want to start over BUT keep the apps that I paid for.


How can I tell if an app was something that I paid for, or not? Is size a first indication?


TIA