Can you post a visual of what you're trying to do?
Otherwise, off the top of my head I'd do this in the same illustrator file (or a copy). Just resize the artboard, then group all of the elements and scale them up by the same percentage. Use the same reference point for both the resize of the artboard and the scaling of the art and they should match right up.
Or, when you export to jpeg from Illustrator, increase the resolution to account for the larger dimensions you need.