See this FAQ entry:

My drawing tools are missing their textures (or show incorrect textures)

Not easily. While I guess technically CC3+ has all the tools required to accomplish this, this isn't a normal workflow the program is made to do, and hence, would have to be done manually, there are no quick shortcuts.

You can use modifiers like endpoint when moving the section to position it precisely, but once it is in place, you need to deal with all those contours. I assume you wish to have them as continuous contours, which means you need to reduce those polys to lines, chop out the pieces you don't need, and join them together again. Not even sure if Combine Paths will be happy with those contours with a huge number of nodes. As an alternative to chopping and cluing together, you could instead use the trace functionality of a drawing tool, and basically create a new contour by tracing the outlines of the pieces that forms the contour crossing the map pieces. This may be simpler. But no matter the method, each contour must be done individually.

Trace can be a bit weird when trying to trace a smooth poly because the nodes aren't located along the visual edge.

Try using Smooth to Straight (right click :CC2EXPLODE: ) on the poly first, then trace it, and turn it back into smooth using Straight to Smooth.

Looked back in time a bit, and found that the references to those files are found in the official DD3 template for CC3. I don't have the actual image files there either, so I don't believe they were never part of the intended install, just leftover references.

The templates for DD3 for CC3+ have been cleaned up, and don't have those references anymore.

For trace to work, you need to be using a drawing tool, not one of the basic shapes from the right hand toolbars, and you need to place down the first node before you can proceed with the trace. There are some types of drawing tools that don't support trace, but all standard straight/smooth/fractal tools should have the trace option.

You can also check out DogTag's trace tutorial video or my command of the week article.