If you are using 3 of 9, you need to prefix and suffix your data with the asterisk (*) character. For example item 128 SDRAM would need to be set up for this barcode as *128 SDRAM*. You can use it, but will need to include the asterisk at the start and end of the variable.
If you can find Code 128, this would be best option to use since it does not require the start/stop code, and produces a smaller barcode.
In either case, you will need to make the font size larger than your standard text font for it to read. If it is too small (compact), it will also be an issue.