Hey buddy..
I think u are confusing between USB 3.1 and PCI-E 3.0.. USB 3.0/3.1 is a serial bus with Teal-blue/Red connectors which can accept any USB devices like External HDDs, etc.. Examples of usb devices, see below:
USB 3.1 is a little faster..
If you meant the differences between, PCIE 2.0 and PCIE 3.0, If the motherboard has a USB 3.0 port it will most probably have a PCIE 3.0 slot.. Also there is almost no difference between PCIe 2 & 3 as far as gaming is concerned..
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