How to import 3d texture?

Hello guys!
How can I import a 3d texture the easisest way and visualize it somehow ( for example as a voxelized thing but other way can be also good)?

I tried to download a 3d texture form different sites like sketchfab.com or from unity assets store but I don’t really know which one is a 3d texture and how a 3d texture should look like.

Any help is appreciated!