40MW = 40,000KW
Typical power density in a colocation facility these days is approximately 5kW per full cabinet (sold as 30A @ 208V or 60A @ 120V at 80% utilization). So, approximately 8000 full cabinets at average density, which would be enough power for one of the 10 largest known facilities in the world. Most likely though, the power density is going to be much higher than typical with bitcoin mining, and could be as few as 1333 actual cabinets at the high end of density of 30kW per cabinet.