GM truck radio swap

Tim R. wrote:

On Thursday, August 3, 2017 at 10:52:23 PM UTC-4, captainvi...@gmail.com wrote:
I have a 2006 Chevy Express van. The radio is the stock Delco AM/FM radio. All my music is on cassettes

I think you're asking the wrong question.

I have an old (1991) vehicle that I use for local transportation in
the knowledge that I have one year left. (each year I decide how
much to spend to pass inspection. I'm not planning on 10 years.)

It seems you've decided your cassettes are worth keeping for another
10 years but your vehicle has one year left so you need to be cheap.
In fact it's probably the other way around.

My wife put an aftermarket radio in our other car for a trip. It has
this weird slot my daughter calls a USB.

USB stands for Universal Serial Bus.
And even then, the USB port (outlet or socket) could be that, or a micro-USB, both of which you use to connect your mobile phone to most computers, wall chargers, audio or video units, etc... via a USB cable.
(a USB-USB or USB-micro-USB cable includes power and data hard-wired connections into one cable)
This hard-wired concept is being somewhat phased-out by Apple and Samsung in favor of both wireless data communications and wireless charging which presents a solenoid situation that cuts down on the wear-and-tear presented by connectors.