when do they find sophia in the walking dead

They find Sophia in The Walking Dead in the midseason finale of season 2, episode 7, titled "Pretty Much Dead Already." After the group discovers that Hershel has been keeping walkers in his barn, Shane opens the barn doors, releasing a horde of walkers. As the group shoots them, a lone walker emerges—Sophia, who has been bitten and turned into a walker. Rick is forced to shoot her to end her suffering. This discovery is a devastating blow to the group as they had been searching for her for a long time.