I've been there, done that with trying to repurpose things I have and sometimes the best course is just to let go and move on. This might be such a situation. How to find out... determine what you want to build as if you didn't have the island, and then see if the things you have fit those plans. If they don't, sell what you have and look for new economically - craigslist and other sources of used stuff are amazing. The unit is a sunk cost; your expenditure won't be affected by what you do with the thing. If you hate it, unburden yourself and then you can build what you really want.

If this unit fits your plans, then the question I'd be most concerned with is height. How tall is the unit, and what surface height do you actually want? The table is too big for the unit to support all by itself - you will need another pedestal or legs that are equally tall. That's not so simple. Are you really looking to actually replace your table with the island? Do you just want extra storage? If that, you could get a shorter storage unit and put casters on it so it rolls under the table... if you build a taller island, you'll need higher chairs.

Anyway, the parameters of the project are probably not clear enough in your post to elecit much guidance, so maybe if you give more info, people can help you out better.

KarinL