Apple® Article - Use iTunes to restore your iOS device to factory settings

When you restore an iOS device to factory settings, the latest version of software is also installed. You can then set up your device as new or restore it from a backup.

Restoring iOS software deletes all data and content (songs, videos, music, contacts, photos and calendar info) from the device.

 

Navigate to Use iTunes to restore your iPhone, iPad, or iPod to factory settings then follow the step-by-step instructions.