Download

See: Update your iPhone, iPad, or iPod touch - Apple Support

Provide further details if above info is not sufficient.

If you have an iPhone 6 or iPhone 6 Plus, you cannot update past iOS 12.4.7.

Tell us what you see in Settings > General > About > Model Number > tap here and tell us the number starting with A????

There is no such thing.

To upgrade you need 50% battery and a Wi-Fi connection.