I want to mount A2212 Brushless motors on my F450 frame. I begin with mounting the X thing on my motor using the set of small screws that came with it. But there are no holes in the frame that matches with the outer holes on X Frame that is attached with the motor. So I figured that I will mount the motors directly to the frame without that X. But the screws that came with it are too short for the need. Can someone please tell me what is its size and from where I can buy such screws "ONLINE" and longer than that. Thanks.

You would need M3x7mm Screws for it.
www.ebay.in/itm/191423972830

No need of the X mounts. These motors needs to be straightaway fixed on this frame using the above Screws.