I Have A 3 Month Old Cockapoo Puppy That Is Pad Trained, I Want To Start To Train Him To Go Outstide, But The ?

last puppy I had was not trained to the pad so I started training him to go outside, but he was 6months old until he really understood, should I wait until this puppy is 6months old to start outside training. Also my dog will pee on pad but will not poop on pad is there something i can do about this.