Could someone tell me how I can place a Market open order for a Future on Natural Gas?

I am trying to back test the following Natural Gas Future from Quandl SCF database "SCF/CME_NG1_OB".

Should my code be using either:

MarketOnOpenOrder("SCF/CME_NG1_OB", numberOfContracts*ContractSize);


MarketOnOpenOrder("SCF/CME_NG1_OB", numberOfContracts);


another method?

If i use numberOfContracts*ContractSize then the number becomes a long not an int, since for natural gas the contractSize is 10,000,000,000.


Appreciate the help.