1In large bowl, mix yogurt and pumpkin pie mix; set aside. In small bowl, sprinkle gelatin over 1/4 cup of the milk; let stand 1 minute to soften.
2In 1-quart saucepan, heat remaining 1/4 cup milk to boiling; remove from heat. Stir in softened gelatin with whisk until dissolved. Stir gelatin mixture into yogurt mixture. Spoon into six 6-oz custard cups. Cover and refrigerate until firm, about 4 hours.
3To serve, run knife around edges of custard cups to loosen. Turn panna cottas upside down onto dessert plates; remove custard cups. Sprinkle with cinnamon. Cover and refrigerate any remaining panna cottas.