I have a toroidal step up step down transformer it only has three wires and a diagram on the side that doesn't mean a lot to me

this was out of a step-up step-down transformer Pictured below that was working fine 250v in 115v out
the problem was the American plugs where not solid enough so i my infinite wisdom a pulled it apart as i do with most things.
but now i cant figure out how to connect it to 220v and get 115v out.

next time i will leave it alone.

3000 Watt 110v Transformers, 220V - 110V Voltage Transformer, Step Up and Step Down, UK to US US to UK Trans formator 3000W


main problem in a nutshell is it only has 2 red wires and 1 black ???