As the Ohio State University link I posted noted, you can see the raster, at least on the bigger ones, with a 10X lens. If I can't see it clearly I check them under a 20X stereo microscope which is relatively low power. The problem isn't so much getting the magnification as keeping them from curling up, if still alive, so you can't see their bottoms
So the stereo microscope allows two hands to wrestle with the grub. You would need good magnification more likely for the small ones like the black turfgrass ataenius but the grubs in question here are way bigger than that.
Edit: I should add that as the Universities of Missouri and Ohio sites I linked to show, the raster of the JB is quite different from June beetles etc. and I think all Frillylilly wants to do is determine if they're Japanese beetle grubs and therefore whether milky spore is an option (although current thinking is that the beneficial nematode Heterorhabditis bacteriophora is probably a more effective option).
