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, still wanting the Cilician legions and not strong enough to maintain himself in this position without them, had to retire over the Euphrates and to seek protection from the cavalry and archers of the king in the wooded ground of Pontic Armenia extensively intersected by rocky ravines and deep valleys. It was not till the troops from Cilicia arrived and rendered it possible to resume the offensive with a superiority of force, that Pompeius again advanced, invested the camp of the king with a chain of posts of almost eighteen miles in length, and kept him formally blockaded there, while the Roman detachments scoured the country far and wide.
The distress in the Pontic camp was great; the draught animals even had to be killed; at length after remaining for forty-five days the king caused his sick and wounded, whom he could not save and was unwilling to leave in the hands of the enemy, to be put to death by his own troops, and departed during the night with the utmost secrecy towards the east. Cautiously Pompeius followed through the unknown land: the march was now approaching the boundary which separated the dominions of Mithradates and Tigranes. When the Roman general perceived that Mithradates intended not to bring the contest to a decision within his own territory, but to draw the enemy away after him into the far distant regions of the east, he determined not to permit this.
Do you see any typos or other mistakes? Please let us know and correct them
Reference address : https://www.ellopos.net/elpenor/rome/5-04-pompeius-east.asp?pg=12