In order to restore your earlier purchases on an iOS device please follow these instructions: open GuitarTuna --> go to Shop --> tap on Restore.
On Android devices, please make sure you are logged in with the same Google email you originally used to purchase the package. Then launch the app and wait for about 2 minutes; GuitarTuna will recognise your previous purchases automatically.
If you've got a Windows phone all the purchases should be linked to your Microsoft Account. Please check the following articles on how to restore purchases on that platform:
Please note that unfortunately cross-platform transfers are not possible.