What advice does Slim give George when George asks Slim about trying to find Lennie instead of killing him?

Towards the end of Of Mice and Men, Slim and George walk into the barn and discover Curley's wife is dead. Curley then enters the barn and says he's going to shoot Lennie for killing his wife. Slim quietly tells George that Lennie must have been responsible for her death even though it was an accident. George then tells Slim that Lennie would have traveled south since they came from the north. George asks Slim if they could find Lennie and turn him in so he could go to jail instead of be shot. Slim tells George that it would be possible if they could find a way to keep Curley from leaving the ranch. Slim says Curley is still upset about his hand and will want to see Lennie die. He then tells George that even if Lennie were taken to jail, he would be strapped down and locked up in a cage. George takes Slim's advice and spares Lennie the experience of being killed by the mob or being locked in prison by shooting Lennie himself.