Maybe an ExpressCard?
Is that the way I should do it?
My ports look like this:
You can use a Thunderbolt dock / docking station. I have added one to my 2011 Mac mini which has no USB 3.0 ports.
There are many docks available and most of them offer USB 3.0 ports.
Keep in mind that, as far as I know, all docks require an external power source (wall plug), but there are some that don't need one.
Please let me know if this answers your question.
This is the product I use:
Belkin Thunderbolt Express Dock for about $200, the predecessor of this version:
Pay attention whether or not a Thunderbolt cable is included. A single cable costs between $30-50.
Instead of a Thunderbolt dock you can also buy a TB to USB 3.0 adapter. Kanex produces one that also supports eSATA. However, you won't be able to connect any devices that need to draw power to operate. Think external 2.5" HDDs/SSDs or USB hubs:
It won't be cheap! Thunderbolt and USB are different interfaces, so active electronics need to exist in the adapter. One of the most recommended options is this adapter from Kanex.
A few other companies offer similar products at slightly higher price points.
For more information on your question, I'd look at this Ask Different thread.