Music format for bringing to audition/demo


Had my system for 20+ years, time for an upgrade. I have not been in a hifi shop since 2000 and at that time I would simply bring CDs. Nowadays is it most common for people to bring digital music on a thumb drive or some other way and what is that? Or do people rely on dealers having nice streamers and they just look up what you want to hear? 

Basically I want to know what it most common and how I can bring music that say I downloaded from hd tracks or similar sites to the dealer. 
nhb1
OK I will just bring some downloaded 24bit songs on a thumb drive, just wanted to check what was common or if there's another way I should know of that's better.  
OK so downloading an HD track then copying it to my thumb drive will do the trick then? I am terrible with computers and want to make sure I don't need some program to convert files, I am noob at this hehe. 
A couple of years ago, or a couple and a half, I went through a few stores bringing my CDs and files on a drive. Wherever I went, except one, they had no CD Player readily available and, at that time, it was the same for USB connected files. In all places, except that lonely one, they brought me an iPad with Tidal and asked what I wanted to hear. It just happened that Tidal did not have what I wanted. In the end, I would enter and ask if they had a CD player, rather than ask to check the speakers I came in for.

The only place that was ready for CD and USB drive was.....Crutchfield.

So, nhb1, bring all you have, but expect an iPad.
Before visiting, call the store and ask what they have available for playback.