I would do this calculation based on the heat dissipation of each miner. For simplyness I would equate the electrical power of each miner with thermal power. So for example if you have 250units and each unit generate 1kw, then you have to move 250kW of heat power out of your container.
So you wanna know the required airflow in a worst case scenario. Worst case scenario is always during summer time. The Delta Temp between the miner and the fresh air from outside should be a criteria. I assume 30°C fresh air temperature.
If the miners should not reach for example 50°C, then you have a delta Temperature of 20°C. Then have a look at this diagram. Its used for finding air flow if you install a compressor cooling like in an ice cream parlor.
So for 1kW and Delta 20°C you need about 175m³/h, multiplied with 250 = 43750m³/h
Edit this example to your needs... I dont know how hot the miners will be and what is your maximum fresh air temperature. If you calculate this for Delta 5°C you need about 150.000m³/h
Cheers