You don't have to buy them again.I have question. almost app if payment completed. (is it called license?) if old device app installed, but need move that license to new device, how to... or just buy that app again? any advice please!
You don't have to buy them again.
When you set up the new device with the same Apple ID that you used on the old one, all you need to to is go to the App Store app, open it and tap the "Purchased" tab:
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Here you'll find all the apps you purchased before with this ID. The ones with a cloud next to them are not installed on your iPad. When you tap the cloud symbol, the app will start downloading and installing on your iPad.
Hope that helps.