Vesa Screw Replacement / Adapter for old Cintiq24HD

I've recently decided to purchase a ergotron arm, but had bought the cintiq so long ago I no longer have the proper vesa mounts / spacers needed to affix the adapter. Does anyone know there proper width / length of the screws needed or the size of the spacers and where I can find them to purchase as replacements? The ergotron arm also came with a 200x100 adapter included but only four holes to mount instead of the 6 on the back of my cintiq... Is there a different adapter recommended? Do I need 6 when the weight of the arm says it can hold 40 lbs? Thanks for any advice in advance.