Just because something is USB3 compatible (or even “SuperSpeed”), it doesn’t mean it has to be fast. That just means the connector has the theoretical possibility of supporting that speed, but the flash drive’s internal memory chips might not be able to read/write that fast. That’s really just marketing fluff – don’t fall for it. It’s like putting race car tires on a crappy car; the engine would never actually put out enough power. Some USB2 drives can be faster than some USB3 drives.
What you need is USB 3 + publicly-verified (NOT manufacturer’s) benchmarks.
Edit: Also, the blue connector is not a guarantee. Some knockoffs will paint their connector blue to just LOOK like USB3, but could be USB2 or USB1. Seriously, look for benchmarks and buy from reputable companies (Amazon direct, Best Buy, NOT eBay or third-party sellers).
Just to explicitly clarify something: Seriously, USB is a complete shitshow.
USB 3.0 is different from 3.1, and both are different from SuperSpeed, and SuperSpeed is different from SuperSpeed+, and 3.0 is actually 3.1 Gen 1, which is different from 3.1 Gen 2, which is different, which are again all different from type C, and none of these guarantee good performance in a flash drive.
Do not rely on the USB logo, connector color, or any words on the packaging (SuperSpeed, Gen 1/2, etc.) to tell you how fast a flash drive will be. They vary a LOT, by a factor of 10x or more. Benchmarks and only benchmarks will tell you what you can reasonably expect.
Arg, sorry, one last time: I completely misread the OP. I thought you were looking for a flash drive. Didn’t realize you already had some and were just trying to verify whether they were USB3.
The simplest way is to do a copy test: if you exceed more than 60 MB/sec, it’s USB3.
Otherwise you can look up their model/serial number online, or plug it in and go to the device manager in Windows and look for their hardware info there. You could find out what kind of chipset it uses, maybe, but that wouldn’t necessarily let you know how fast they are, just what their theoretical maximum (which no flash drive really reaches).
Alternatively, you can download USBDeview which is a handy utility that gives you lots of detailed information about connected USB devices. It will tell you for sure what USB protocol a given device is using.