Proper workflow for importing TreeCreator trees from a project built in Unity v3.4.x

Greetings all,

I'm hoping this is the best sub-forum to post this question, though if this is not the case, anyone should feel free to point me in the right direction.

In any event, I am converting an old project (last updated in Unity 3.4.0) to a more current version (2018.x) for VR. The project has a wealth of trees created using the legacy Terrain/TreeCreator tools. While I've had success importing the most of the other assets, the TreeCreator trees have been troublesome. Wondering if anyone could point me to a good tutorial or two on this topic.

A few notes:

At this moment, I'm pretty agnostic about the overall shader approach of the project, in other words, I'm willing to keep to using the legacy shaders if doing so will save me enough time in the long run versus converting the entire project to use the more contemporary "Standard" shaders.

I've done one test where I'd selected a collection of TreeCreator trees in the old project, created a Prefab of them, exported the prefab as a Package, and imported the Package into my new (v2018) project. No idea where I err'd here but, but after importing the package, and pulling the assets into my Hierarchy, of the 20 or so trees that I'd imported as prefab, only a single one included all its requisite data (geo, shader/texture, and procedural info). The remainder of them came in as only transform coordinate data.

I assumed that perhaps the migration method described above didn't account for the data files that Unity creates whenever you create an asset with TreeCreator, so I then copied anything that looked like it could be a TreeCreator-related file from the Assets folder of old project to Assets folder in new project. I then re-launched Unity, however this did not do what I thought it might, which was perhaps update the links to each TreeCreator asset, thereby showing the full trees, rather than empty nulls.

Any advice is massively appreciated!
NpF