Upscaling of low poly geometry to highpoly while keeping shape/watertight mesh

I have a model created in sketchup of an organic shape, it was created with smoothing turned on so after it was finished I realized that it wasn't high poly.
I need the model upscaled while keeping the shape and the model needs to stay manifold.
Upscaling of low poly geometry to high poly while keeping shape/watertight mesh.
I need you to do this in 3dsmax or meshlab or in any program that can output a .dae file or .3ds or similar format.
I need you to be experienced with 3d modeling.