This question already has an answer here:
I am an Indian citizen who lives in the USA, travelling from USA to India through ROME FIUMICINO, ITALY airport and returning from India to USA through the same airport in Italy. I am travelling with an advance parole document and don't have a visa stamped in the passport. My stopover is around 3 hours. Please advise if I need a transit visa for Italy or can travel to the USA (on return) based on approved advance parole.