How to convert for import/slice this file? (fbx / glTF)  

How to convert for import/slice this file? (fbx / glTF)

Not sure if this is the right place.

I would like to print this model ( https://sketchfab.com/3d-models/fagradalsfjall-volcanic-eruption-26062021-b53ddf3dd1ce45bfbfaf22c1a062d116) but it is only available in .fbx and .glTF. After searching about conversion, I tried a few different options, including Greentoken. Only one site worked. (I can't attach the STL because it's 100+ MB, let me know if there is a good way to provide that.)

When I pulled the STL into PrusaSlicer, I could see it's a very thin surface, and it did not slice correctly as a result. I downloaded Blender to see if I could work with/fix the STL, but it did not recognize the STL file.

Thinking perhaps I need to try converting to STL again, I found a recommendation to use OpenCAD to convert from fbx, but it did not recognize the fbx file.

I don't know enough about fbx or glTF to understand if there is something wrong with the file I'm working with, or whether it's just difficult to convert from these formats to something I can slice. Can anyone recommend a tool or process I should use?

Many thanks.