Hello
NycoT
Regarding the purchase itself, it is linked to your account. For example if you use an Android phone, your purchase is attached to your google account, so unless you create a new account you will automatically keep it. The purchase automatically restores itself when you configure your new phone. Note that if you switch from Android to Ios you will lose your purchase though.
For the data itself, all your progress are saved in this directory (assuming you use an Android phone):
So under your Android directory, in com.StefMorojna.SpaceflightSimulator/files.
Your data is under your
Saving directory, and you have to keep your
Custom Solar Systems if you downloaded some planet packs.