You must have a backup of your important information for use, in situations where your device is ever replaced, lost, or damaged. Moreover, if there is no Back Up installed on your iPhone, iPad, or iPod touch, recommend to create Backup prior updating your devise to iOS 13 or iPadOS.
Step-2. Update to iOS 13 or iPadOS
You can update your iPhone, iPad, or iPod touch to the latest version of iOS wirelessly or in case if you can't update wirelessly then you may use your computer to get the latest iOS updates.
Step-3. Update of an Apple Watch
Those having an Apple Watch Series 3 or later may proceed to update to watchOS 6, provided your associated iPhone is updated to iOS 13.