CC's and Horsepower are like apples and oranges. CC's are a unit of volume and horsepower is a calculation of work load. Only a dyno would be able to tell how much horsepower a given displacement will/would make.
There is no conversion. It depends on too many factors to directly convert between engine volume size and horsepower.
If its a new engine, you should have no problem finding the rated horsepower and volume information online from the manufacturer. Otherwise you would need to take the engine to a shop and have it measured.