Apple regularly release upgrades for all devices and it is recommended as & when these are released users upgrade & especially when security patches are released as this protects you, your data & your device.
To upgrade your iPhone or Ipad follow the below guide
1, Select Settings on your Ipad or Iphone, you should then see a screen that looks a lot like this open then select “General” which is positioned above Control Center as seen in this photo.
2, Now you have selected “General” another screen should load which looks like this photo, select “Software Update”
3, Your device will now attempt to check to see if you are on the latest version of iOS. If you are not on the latest version is will ask you to upgrade & it is recommended your device is plugged into an outlet when doing this.
Note you must have an Internet connection to check to see if an update is available for your phone.