Mh, from that the only readable thing is that you have a ThinkCentre M82
, if that's true, it's not meant to be upgraded like that.
So we are back to your idea about hubs and the 4 back ports. A hub splits the bandwith of a single port (the port it is connected to) with all the devices you attach to it, so if you connect say 2 hard drives and use both at the same time, (say a large file transfer on both at the same time) the speed is cut in half, or worse.
Also, the power a hub can provide to all the devices attached to it is limited to the one it takes from a single USB 3.0 port, unless it has its own power supply.
Since you are not going to be able to reach the backside ports easily anyway, I'd suggest to buy extension cables and pipe all (or a couple of) your backside ports in easy-to-reach places. Some extension cables are designed with this use in mind, like this
, but cost twice as much as a simple USB 3.0 extension cable
Just make sure the stuff you buy has one Male and one Female connector, or you won't be able to connect any device to it (Female is the connector like the one in the back ports of the PC you have).
For the sake of others that may read this in the future, the pin end must me connected to the motherboard directly, on motherboard USB 3 headers you can still use the rear ports for something else. The headers on the mobo look like this
If you buy the components and assemble the PC on your own, you are 99% likely to have at least one 2-port header.