if you find such an adapter that actually works for USB 3.0, my money is that it will only work for USB 3.0 in one orientation of the USB-C plug, falling back to 2.0 in another. Two of this ...
and most adapters and hubs have at least one for your non-USB-C memory sticks and drives. Look for at least USB 3.0, which has a speedy bandwidth of 5Gbps compared to the lamentably sluggish USB 2 ...