After the battle of Pharsalus, Caesar did not at first know whither Pompey was gone.
"The Great Events by Famous Historians, Vol. 2" by Various
Accordingly, he offered battle to Caesar in the plain of Pharsalus, or Pharsalia, in Thessaly.
"A Smaller History of Rome" by William Smith and Eugene Lawrence
At the age of seventeen he served with Pompey in Greece, and commanded a squadron of cavalry at the battle of Pharsalus.
"Encyclopaedia Britannica, 11th Edition, Volume 6, Slice 3" by Various
After the battle of Pharsalus, he was commissioned to transport some recently levied troops to Illyricum.
"Encyclopaedia Britannica, 11th Edition, Volume 11, Slice 4" by Various