Please when I tap on software Update nothing appears on my iPhone

There is nothing to solve.

Check Settings > General > Software Update

You will see a message that you already have the most recent update for your phone. It cannot be updated any further.

If you have an iPhone 7, you can update to iOS 15.7.6

If you have an iPhone 8 or higher, you can update to iOS 16.x

The iPhone 6 Plus can be updated to iOS 12.5.7, no further.