In which year of King Josiah's reign did the word of the LORD first come to Jeremiah?

Answer: The thirteenth

The word of the LORD came to Jeremiah in the thirteenth year of the reign of Josiah son of Amon king of Judah.

“The word of the LORD came to Jeremiah in the thirteenth year of the reign of Josiah son of Amon king of Judah,”— Jeremiah 1:2 (BSB)