If you have an iCloud account, your iPhone and iPads back-up their contents there. However, to be doubly safe, you should make an iTunes backup of your device on your Mac. Here’s how:
Connect your device to your Mac.
Open iTunes (makes sure you have the latest version).
Choose your iOS device.
Save content that you downloaded from the iTunes Store or App Store this way: Click File > Devices > Transfer Purchases.
Wait for the transfer to finish.
If you want to save Health and Activity data from your iOS device or Apple Watch, you’ll need to encrypt your backup. Select the box called Encrypt [name of your device] backup and create a password.
Be sure to write down your password and store it somewhere safe, because there's no way to recover your iTunes backups without this password. If you don't need to save Health and Activity data, you can make a backup that isn't encrypted. Just click Back Up Now.
After the process completes, make sure that your backup finished successfully in iTunes Preferences > Devices. You should see the name of your iPhone or iPad, along with the date and time that iTunes created the backup. If you encrypted your backup, you should also see a small lock icon beside the name of your device.