Open Settings ➔ General ➔ Software Update and see whether that update appears and then choose to install the update. If you cannot update then see below:
Make sure that your iPhone is setup to meet the following requirements before you attempt to update the iOS version-
- Your iPhone must have a fast Wi-Fi connection; you cannot update over cellular data or a cellular hotspot
- The iPhone can not be in Low Power mode
- The battery state of charge must be above 50%
- Your iPhone must have at least 6GB or more free storage space
- Your iPhone cannot be connected through VPN
- You should leave the phone plugged in until it finishes updating, both to assure that it remains above 50% and to keep Wi-Fi enabled (Wi-Fi turns off when the phone sleeps if not connected to power).
Once you have figured out the reason for your iPhone not updating and have updated your iPhone, then you can Transfer Data from old iPhone to new-
Do you have a backup created either on iCloud or on your computer?
Method 1 - Backup your old iPhone on your computer like this ➔ How to back up your iPhone, iPad, and iPod touch - Apple Support and then Restore your new iPhone from that backup like this ➔ Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Method 2 - The Quick Start method and here is how to do that ➔ Use Quick Start to transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support
Axel F.