If you've changed devices, you can sign in on your new device using the account that originally bought the apps and download them again for free. You will not be charged twice for the same app if you are using the same account (Apple ID or Google ID).
The process is the same as if you deleted an app. This article shows you how to get your apps back.
Please Note: apps are not transferrable between iOS and Android. If you were using one operating system and are now using another, please read this article.