I mentioned that the motherboard of my recently-acquired second-hand PC only has USB2 sockets. For attaching my external USB3 hard drives, it is preferable to have a USB3 socket on the PC -- a couple of them work with USB2, however my 2TB drive requires a USB3 socket.
Forum member Feodor recommended to me a PCI-E USB3 card available online.
I looked around online, and found one of the cheapest is MSY, which has store outlets in major cities of Australia. It only cost AU$20, so I bought it: