Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Pompeius Proceeds to Colchis
Pompeius now, agreeably to the plan which he had formerly projected, marched through the Sarapana pass from the region of the Kur to that of the Phasis and thence down that river to the Black Sea, where on the Colchian coast the fleet under Servilius already awaited him. But it was for an uncertain idea, and an aim almost unsubstantial, that the army and fleet were thus brought to the richly fabled shores of Colchis.
The laborious march just completed through unknown and mostly hostile nations was nothing when compared with what still awaited them, and if they should really succeed in conducting the force from the mouth of the Phasis to the Crimea, through warlike and poor barbarian tribes, on inhospitable and unknown waters, along a coast where at certain places the mountains sink perpendicularly into the sea and it would have been absolutely necessary to embark in the ships-- if such a march should be successfully accomplished, which was perhaps more difficult than the campaigns of Alexander and Hannibal-- what was gained by it even at the best, corresponding at all to its toils and dangers?
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Reference address : https://www.ellopos.net/elpenor/rome/5-04-pompeius-east.asp?pg=20