There is no clear answer to this question. It depends on your goals, body type, and activity level.
If you want muscle gain, you should aim for 1-2 protein shakes daily. If you are trying to lose weight, you may only need one protein shake a day. You may need 2-3 protein shakes daily if you are active.
Remember, there is no 'correct' amount of protein shakes that you should be drinking a day. The only important thing is that you drink enough so that it becomes a habit and you don't feel deprived.