How to make existing classes to be a class template?

For example, I have several existing point classes for 2D (two-dimensional) and 3D cases, like class Point2D and class Point3D. And I want it to be templated like template<int D> class Point where Point<2> is equivalent or directly use Point2D and Point<3> is equivalent or directly use Point3D. I don't want to reimplement those existing classes since my real classes are not as simple as class point. Any way to do it?