VISA VXI Cmd or Query Function

Hello, I'm trying to use the VISA Query Function to issue queries and receive the response but I'm not sure how to do this since the function description says "command" or query is just 32 bits. Also the "command" is numeric, I assume binary, how would I convert a string to numeric?

Here's a link to the function documentation: http://zone.ni.com/reference/en-XX/help/371361L-01/lvinstio/visa_vxi_cmd_or_query/

Thanks.

-Justin