You can set the stroke to dotted. If you need to grab the outline of a group of objects, you can use Shaping>Boundary.
@David Bevins I want to make dotted worksheet of clip art pictures. How can it possible? How this elephant clip art's outline make in dotted form?
I was assuming you were working with a vector image. Being that it is a bitmap it has to be recreated as vector to use the stroke method I was describing.
As it is a low resolution bitmap, the autotrace might not give good results. Some time in PhotoPaint might be able to enhance it in a way that the autotrace would work, but it is not immediately clear to me what would give the best results. I would have to fiddle a great deal with it, trying feathering and blurring to get something cleaner for autotrace to work with.
All in all it might be easier just to redraw it with the bezier pen/tool. It can be done in 15-30 minutes. Then you would have a vector object to work with.
Here I just did a rough outline to illustrate. Its not to clean as I just sped through. But you can see I outlined the elephant with the bezier pen, giving me a straight lines around. Then adjusted each segment to curves, then gave it a dotted stroke. I didn't do the toes, ears eyes or back leg. More care would give better results.
There is not an easy button to push for this. It is going to require redrawing by hand, or man handling the autotrace to give a good result. It would be great if you could find vector clip art instead of raster to begin with.
One might be able to get good autotrace results if you used tracing paper and a marker to draw the image, scan with a scanner, and try autotrace on that.
Five minutes after I posted, I remembered centerline trace, doing a centerline trace, with detail cranked up high, then give a dotted stroke to the results gave me this. A little rough, but maybe good enough.