What size (not wattage) Power Supply will fit in this case?

[carrierPigeon]

I plan to buy this case:
Enermax Fulmo.Q ECA3361
https://www.staples.com/Enermax-Fulmo-Q-ECA3361-Computer-Case/product_IM19D1601

Here is some info about very similar models from the manufacturer (though I couldn't find the exact model):
http://www.enermax.com/home.php?fn=eng/product_a1_1_1&lv0=2&lv1=9&no=269
http://www.enermax.com/home.php?fn=eng/product_a1_1_2&lv0=2&lv1=9&no=269

What physical size should the power supply be?

Is it supposed to be some sort of ATX size because that's the size motherboards that it fits?

 

[pendragon1]

yes atx