I purchased an Adobe stock vector image that is made of multiple layers that are laid over with transparency to get the color darker etc — as seen below. How do I reduce in Illustrator multiple layers that are creating a different color through transparency into one Layer with the color created? If I use Pathfinder it just splits the layers but does not reduced it into one. Is it even possible?
Depends what you mean by "layers"... What you see in the Layers panel in Illustrator is actually layers and objects, so probably not; all of those shapes need to be separate objects.
As for reducing the transparency down you can do that. Just go to:
Object → Flatten Transparency...
That'll flatten all the transparencies, blending modes and colors to what you see so all you'll have left are solid colored shapes, rather than blending transparent shapes.