How to tell what version iPhone I have?

How to tell what version iPhone I have? - 1

Option 1: Look on the back of the iPhone for a model number (not all iPhones have this listed on the back)
Option 2: Go to settings > general > about > legal > regulatory (not all iPhones have this built into the software)

You should find a model number (e.g. A1533). Once you find the model number, google that number and you should find a screen telling you what iPhone you have.

Well you should know since it's your phone, but if you can't figure it out for some reason, do what Chad said.

Settings… About phone

Usually just looking should tell.

Otherwise
https://support.apple.com/...s/HT201296

Go To Settings >>> About Phone and The version Number should be right there!