iPhone SE not being seen in iTunes

I have had to buy a new iPhone when my iPhone 7 inexplicably died and could not be revived.

I decided to buy an iPhone SE and all has went well so far until I come to connect it to iTunes to download a tone or two and photos to be used as wallpaper etc.

My iMac is running Sierra 10.12.6

My iMac is a 2015 model so only has two Thunderbolt ports and 4 USB ports in the back

The iPhone comes with a Thunderbolt 3 to Lighning cable so I can't easily connect.

I have used a USB to Lightning cable and when I first plugged my iPhone in I was asked to Trust this computer, which I did but the iPhone did not appear in iTunes.

Now when I plug the phone in, iTunes opens, the phone charges but it does not appear in iTunes.

I can't work out why it isn't working so thought I'd ask the Community in case I am not the only one with this issue

Thanks in advance

Al