I'm not really sure how to translate "au pas" because it can be translated in a bunch of ways depending on how it is used and which words accompany it, so I've opted for "to the pace" because that is the general idea behind that expression. I also assume the japanese オパオパオパ is just meant to reproduce the pronounciation of "au pas au pas au pas", but please fix it if it has another meaning.
In stepin stepopa opa opaOpa is how you pronounce "au pas" in frenchin step