Hi Labviewbeginner,
it's always a very good start with "Find Examples" in the Help-menu. In my LV 7.1 I find the appropriate examples in "Harware In- & Output"->"Serial". A very good start would be "Basic Serial Write and Read", there you can send some String to the modem and after a customizable delay read the answer. If You right-click on the String- control & indicator, you can select "Hex- Display" to input or read your string in hexadecimal notation.
Hope, this helps,
Dave
Greets, Dave