If you're looking for a Tamil dubbed version of "Koi Mil Gaya", I recommend checking out legitimate streaming platforms or purchasing a DVD/ digital copy from authorized retailers.
Released in 2003, "Koi Mil Gaya" is a beloved Bollywood film starring Shah Rukh Khan, Preity Zinta, and Sushma Swaraj. The movie tells the story of Rohan, a young man with mental disabilities who befriends an alien and learns to overcome his challenges.