What the others say. Thunderbolt is a Mac thing, and there's Thunderbolt 2 and Thunderbolt 3. There are very few Thunderbolt 3 interfaces and they tend to be on the very pricey end of the spectrum. Some Thunderbolt 2 ones are out there, but you need an adapter to use it with a Thunderbolt 3 port.
USB-C is more common and affordable, and is compatible with Thunderbolt 3. That's the route I went, and if you're actually on a PC, probably what you really mean. Note that USB-C does not necessarily mean USB 3.0, which is the really fast connection. It needs to be USB 3.x capable at both ends, physically, and also supported in the driver. It's very fast.
I have a Steinberg UR44-C. Seems darn quick when switched to USB 3 mode. (N.B. It is that it is not class compliant at USB 3.0, so you have to use the Yamaha/Steinberg driver on OS X.) At least one credible review shows that this line of interfaces is a bit noisier than others in the same range, but the ones currently in the same price band do not have USB 3.0 - or at least didn't a couple months back when I was shopping. I think supply of interfaces is still a bit squeezed, but getting on a waiting list seems to work.
One thing about USB C is that it *may* support higher voltage/amp output (Power Delivery). My UR44-C can run off the Thunderbolt 3 port on my iMac and supply phantom power to all 4 mic preamps. Most 4-channel/pre interfaces cannot run on USB power. (I had an older USB 2.0 M-Audio that could, but would shut off inputs 3 & 4.)