Well, I think this is the right board to post on, i dunno

So I bought this hub dynamo from the internet last week, it was on sale, and it just arrived today. It's just the hub and I've never ever messed with a bike's rims or spokes, so I have no idea how to replace my old hub with the dynamo one, but I think I can manage that watching videos and stuff.

What I want to know is, if I have a 28 inch rim, can I use the same spokes my wheel has or do I have to buy new ones? The distance between the rim and the holes where the spokes go seems longer on the old hub, while on the dynamo hub it seems closer. Can I just arrange the spokes in another order so I won't have to buy new ones?