If your local VRS is set to port 310003 (I think you may have one too many 0’s) for MLAT then I think you should be set. If you wanted to try the Co-Op VRS in addition to local VRS, the command would be
sudo piaware-config -mlatResultsFormat "beast,connect,localhost:30104 beast,connect,feed.adsbexchange.com:30005 basestation,listen,310003"
sudo piaware-config -restart
If MLAT isn’t working with local VRS, try mgunther’s excellent tutorial: http://discussions.flightaware.com/ads-b-flight-tracking-f21/vrs-show-both-dump1090-adsb-and-fa-mlat-positions-t36086.html