Take the old one off and see if there's a part number on it. Google should then be able to find it. Failing that once it's off take a couple of photos and post on here. Someone is bound to know which type it is. There are, as I'm sure you're aware, an endless array of different freehubs so don't order one until you're 100% sure which one it is. Have you removed one before? If not there are loads of videos on YouTube. Some just pull off, others you can remove from the front, others from behind. Sadly no such thing as a 'standard' freehub.