Your kyu rank is relative to the style (and dojo) that you practiced at when you were 15. Realistically, no matter what the style 9th kyu is barely more than beginner.
I'd suggest you start again from white belt (whatever kyu that happens to be in the dojo you'll be attending). If you remember stuff then you should be able to advance fairly quickly. I've trained at other dojos as a white belt even once I had my black, it can be enlightening getting back in at that level.