The files are only split into effects. So all related files are part of the same animation are part of the same PNG. In the visual/Sprite/Effects folder. Originally all sprites were in the same file I separated each effect out and it seems to work well with unity. Is there any reason you want each effect broken up into a PNG for each frame? I could recommend some programs that could split them for you but it seems to work fine as is...
Or gimp or Photoshop can split for you. Or I could if you really want me to