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
Hannibal, who after the passage of the Rhone had in a great assembly
of the army explained to his troops the object of his expedition, and
had brought forward the Celtic chief Magilus himself, who had arrived
from the valley of the Po, to address the army through an interpreter,
meanwhile continued his march to the passes of the Alps without
obstruction.
Which of these passes he should choose, could not be
at once determined either by the shortness of the route or by the
disposition of the inhabitants, although he had no time to lose
either in circuitous routes or in combat. He had necessarily to
select a route which should be practicable for his baggage, his
numerous cavalry, and his elephants, and in which an army could
procure sufficient means of subsistence either by friendship or by
force; for, although Hannibal had made preparations to convey
provisions after him on beasts of burden, these could only meet for
a few days the wants of an army which still, notwithstanding its great
losses, amounted to nearly 50,000 men.