iPhone 5 is charging but not recognised by MacBook air

It is always painful when everything seems all up-to-date but still nothing work. I am running the latest software on an old computer and an old iPhone. I just bought an iPhone 11, thinking to do some back up on iPhone 5 before I make a big move. But iPhone 5 is not recognised by my MacBook air but it is charging.

1. iTunes does not recognised iPhone 5, so I cannot back it up there. iTunes version 12.9.5.5
2. Checked system report, USB 2.0 and 3.0 but none of them can see iPhone connection.
3. I reset all setting on iPhone 5, it says OS uptodate 10.3.4. It is rebooted.
4. I restarted Macbook air. It is 2012 model, with MacOS Majove 10.14.6, the latest.
5. I used two USB - lighting cable, old and new. I tried them on two different USB ports. iPhone is still giving the same response, it is charging when connected to MacBook air but it is not recognised.

I am desparate to back it up so that I can use my new iPhone 11. But what has gone wrong here. Please help!!!