Resetting Old iPhone
I just bought a new iPhone and all data has been uploaded to it. Will resetting my old phone delete any information from the new one? Is there anything I should know before resetting the old one?
iPhone 6s, iOS 12
Do not manually delete anything from there.
Head to Settings > General > Reset > Erase All Content and Settings.
It will remove all of your information and settings from the iPhone, but your new one will be fine.