I'm doing some stuff to share a hair style for Jinryuu's DBC/NC mods, but I need pictures of it. I haven't been able to find the screenshots folder, or even the .minecraft folder! I am using Windows 10.
Search %appdata% in the Windows Search Bar, then go to the .minecraft folder (should be near the top) and in that folder there should be a screenshots folder!
You could also put this in the directory bar:
Replace USER with your Windows Authentication username.
Also, if necessary, change C: to whichever drive you're using (ie: C:, D:, A: etc.)
This should bring you directly to the Minecraft Screenshots folder.