1. Open up Report Writer. GP > Tools > Customize > Report Writer.
2. Open the report you want to modify (modified reports are in the right column). Click on layout.
3. Go to the toolbox window (click windows > toolbox if you don't see it.
4. In the blue dropdown, select calculated fields. Click New if you want to make a new one.
5. Give it a name and change Result Type to String.
6. In the Expressions Calculated Box, you want to insert in the code. It must be like the format below, just replace the data in the parenthesis with the data field you are trying to insert
"*" > Just type a * in the constant box
# > The CAT operator
STRIP > Located under functions
SOP_HDR_WORK.SOP Number > The table.field for the data (located under fields)
7. Hit ok and drag the calculated field on to the report from the toolbox.
8. Click on the data you just dragged and go to layout > properties.
9. In the properties window, change the font to 3 of 9 barcode. Adjust any other settings and save the report. It should be able to be scanned now. May need to add the barcode on the report header and page header (see two barcodes below).
More info below:
https://www.erpsoftwareblog.com/2013/06/add-barcodes-to-report-writer-in-gp/