It's used as a classifier, like this:
So how to say it in English?
Generally it's called 'move'.
To be precise, 招 is 'move' and 式 is 'stance' or 'form'.
When it comes to a specific move, you can use words like catch (手 as in 擒拿手), hit (打), reach (长拳), kick (踢) etc.