Index match on two sheets

Hello,

I have a formula right now where I use index match to get a specific value on another sheet.
However, I would like to look on two sheets. Whenever I select two sheets in my formula, it does not work. Cannot figure what I am doing wrong.

When value 6 is inserted, the result should be 111 from Sheet3. However, if value 3 is inserted, the result should be 33 from Sheet2

Any help is greatly appreciated.