Your Samsung Galaxy Tab does not accept the normal sized USB.
You therefore need one of the Convertors which Plug Directly into the Charging Port on your Tablet and allow a Normal Male USB to be plugged in.
Use this for MANY things including plugging a Keyboard in.
We sell 7" and 10" Keyboard Cases and we also sell Wireless Keyboard and Mouse Boxed Set. Click here to see them - https://stores.ebay.co.uk/Tablet-Chargers-and-Cases-Shop/_i.html?_nkw=galaxy+keyboard&submit=Search&_sid=40297490