It was mounted with lag screws on my BF from the factory - but lag screws through fiberglass and into wood. If you have metal to go into, I would tap it and use machine screws or hex bolts.
Another thing to consider: if this is the typical hook bracket that the top bale of the steps hook onto, you may want to consider a more secure mounting arrangement. In my opinion many of the complaints about scissors steps stem from this mounting scheme, which allow the top of the steps to wobble. I have mounted mine securely at the top on the last two campers, and it makes a big difference on how secure and stable the steps feel.