idem apud Mogontiacum tribunus legionis sextae Gallicanae Francos inruentes, cum vagarentur per totam Galliam, sic adflixit ut trecentos ex his captos septingentis interemptis sub corona vendiderit.
Translation :
Likewise, when at Mainz as tribune of the Sixth Legion, the Gallican, he completely crushed the Franks, who had burst into Gaul and were roving about through the whole country, killing seven hundred of them and capturing three hundred, whom he then sold as slaves.
Edition :
Historia Augusta, Volume III: The Two Valerians. The Two Gallieni. The Thirty Pretenders. The Deified Claudius. The Deified Aurelian. Tacitus. Probus. Firmus, Saturninus, Proculus and Bonosus. Carus, Carinus and Numerian. Translated by David Magie. Loeb Classical Library 263. Cambridge, MA: Harvard University Press, 1932.
Notes :
Aurelian also captured and sold some of the franks as slaves. described in: "Aurelian and his soldiers capture 300 Franks and sell them into slavery."