Assuming that your traffic figure is for the busy hour, divide it by 36 to convert to Erlangs (33.333). Then, use our free online Erlang B Calculator, setting the blocking as 0.01.
The answer comes out at 45 lines.
We also sell a Windows version of this calculator for 80 US Dollars for a single user licence. This also includes an add-in for Excel that allows you to perform these calculations within a spreadsheet. Click here for more information. I have attached a screenshot of the Windows product to this message.
Please feel free to contact us if you require any further information.