Start by looking at the manufacturers details for the scale you are using: it should include the important details about the interface such as speed, bits per character, parity, and so forth, as well as the data format it is using - and there is no guarantee that it is "standard" in any way - which is why your first stop should be the manufacturer.
Then ensure that it works to your PC by connecting it and using HyperTerminal or similar to make sure that communications are working using the details from the manufacturer.
Then look at using the
SerialPort class[
^] - the link includes an example - which will let you start to form that communications with your code.