Answer: He returns to the image of himself as a young boy.
Explanation:
"This is what I say to the young Jewish boy wondering what I have done with his years." is the phrase that is showing us that Wiesel is using his image when we was a young boy.
Rhetorical devices are used to inform or impact the ones that are reading or watching, in this case audience that is listening to his Nobel Prize speech.
With this rhetorical device he is awakening the audiences emotion and the people are feeling close to him because they are listening about a part of his life.