Need to update my iPhone

Your tag line says that you have an iPhone 6 running iOS 12.

Apple released that iPhone ten years ago. At the time, it was running iOS 8. It got four major version updates, but iOS 12 is the end of the line. You cannot update an iPhone 6 to iOS 13 or beyond. If you need to run modern apps, it is time for you to replace that phone with a much newer phone – preferably one that is compatible with iOS 18.

iOS 18 - Apple

Available iOS updates depend on the supported, built in hardware for each iPhone model.

The iPhone 6 can not be updated any further than the latest iOS 12 version.

iOS 13 and iPadOS are compatible with these devices - Apple Support

iOS 14 and iPadOS are compatible with these devices - Apple Support

iOS 15 and iPadOS 15 are compatible with these devices - Apple Support

iOS 16 and iPadOS 16 are compatible with these devices - Apple Support