SMac770

So you're saying you have the 30-pin iPhone AMI cable and then you have some 30-pin iPhone plug to USB plug cable? When you say it didn't do anything, what did you do to try and access it? Did you press the Media button until the AMI entry came up? Also, what phone and OS version are you running?
I suggest you get the actual AMI aux cable if that's what you want, or maybe a Bovee Tune2Air Bluetooth AMI cable if music streaming without having to plug in a cable all the time is desired (Bluetooth streaming is only built in on the B8.5, 2013-2016 in the US, vehicles with MMI/Navigation). Lot of people also run an aux extension cord from the AMI aux cable through the plastic work so it's sitting wherever they like to keep their phone.

https://parts.audiusa.com/accessorie...unication.html
Second entry is the AMI aux cord
https://www.genuineaudiparts.com/oem...ble-4f0051510t
Not cheap; you can find knock offs on eBay no doubt. But for a one time purchase, I prefer problem free legit product.

Further down, you see more AMI cables. There's a lightning one if you have a modern iPhone, or a microUSB one for an Android phone. The "iPod" one, the legacy Apple 30-pin plug, is likely what just came with the car and is probably what you have currently. If you're looking for Bluetooth streaming, this is what I would try first, https://www.viseeousa.com/collection...-mdi-connector