Download to what device exactly?
If you have a recent Mac the Finder should be able to detect the iPhone directly.
Current Macs cannot download older version so of iTunes, but as mentioned should not need to.
If doing this on Windows, the current version of iTunes or the Devices app should also work just fine.
If you need an older version of iTunes for Windows for some reason you can find them in the following user tip by scrolling down to the Installers section.
click here ➜ Troubleshooting issues with iTunes for Windows - Apple Community