There are also other simple ways to confirm usb2.0 or usb3.0 port:

1. Check usb port logo of computer. usb2.0 & 3.0 have differ usb logo.
2. Download or upload a fixed size file. After transaction completed, statistical information would be showed including data size, speed and time. usb2.0 and 3.0 have different speed limit.

For example:

C:\Users\jason95>adb root & adb remount

adbd is already running as root remount succeeded

C:\Users\jason95>adb pull /data/test.img

/data/test.img: 1 file pulled, 0 skipped. 323.9 MB/s (1073741824 bytes in 3.161s)