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While Andrea's solution will certainly work, the one I offered will replace the SYMBOL fields with the actual em dash character, which I think will be more satisfactory in the long run. You must have field codes displayed in order to use that Replace sequence, as the code ^19 is the opening field delimiter (the thing that looks like {, an opening brace character).
This will replace the character found with an em dash in the Default Paragraph Font (your SYMBOL field specifies Times New Roman as the font, meaning that your dash might not match surrounding text if it is in a different font). The only reason for using this SYMBOL field would be that the Default Paragraph Font is one that doesn't contain the em dash character, and those must, these days, be vanishingly rare.