@Athena French translates "I have the power" by "Je détiens la force toute-puissante!" ('I own the all-mighty power'), which is more pompous and convoluted, but very classy nonetheless.
I don't know how they could have translated it in a more straightforward way honestly. The literal translation of "I have the power", "J'ai le pouvoir", would mean either "I am in charge!" or "I am able" (to what?), which either makes He-Man a megalomaniac, or doesn't make sense.
I'll definitely check it out. I used to watch it as a kid. 😏