strokes around Numbers that are 3d.

Not sure. but may be you mean this? You need to add stroke in appearance panel

I guess you'll have to rasterise it (or at least, rasterise a copy) and go to to object>path>outline stroke. But we don't know how your artwork is built, so a screenshot would be very welcome! 🙂
and possibly with the artwork and the layers panel + 3D panel showing, so that everything we need is in one image.

defaulty,

As I (mis)understand it, you have, or can make, a Group of fill/nostroke paths, and you wish to have a simple separate stroked path round everything.

If that is true, you can select the group, then Add New Stroke in the Appearance panel, then Object>Expand Appearance, then select the stroked paths and Pathfinder>Unite.

Edit: Hi Hans-Jürgen, sunny and almost springlike here today, after many autumnal days.

Please show something.