Last year or so I bought the game Sid Meier’s Pirates from developer 2K it is not supported anymore how can I get a refund ?

There aren't refunds. Have you contacted the developer to see if they have any plans to support iOS 11 ? Though as they haven't done so in the 18 or so months since they've known that they would have to make changes it's probably unlikely now that they will do so.

Refunds of that nature can only be obtained via the developer. Had you bought it from iTunes you could have asked Apple via the 'report a problem' system but you should appreciate, Apple cannot be responsible for a developer's failure to update their programs.