Im very confused by how many reps per set to do for an underweight guy looking to build muscle mass?

I'm 6'3 and i weigh in at just 150 pounds so Im a few pounds underweight. I hear that being very thin while lifting weights has the advantage because the real skinny people tend to look the best after they get muscle results, needless to say. Anyway, I want to start taking up weight lifting to gain some muscle onto my very skinny frame, but I am just so confused on how many reps per set to do. Ive already got a 3 day full body workout routine set up with 3 sets in each exercise,but how many reps per set to see the quickest, most attractive muscle-gaining results possible? I hear do 10-12 reps,I hear do 4-6 reps, 3-5, all kinds of things! But which should i actually follow for optimum muscle mass gain?Im very confused by how many reps per set to do for an underweight guy looking to build muscle mass?
Best is heavy weights 4 to 6 reps. and resting 1 to 3 minutes between setsIm very confused by how many reps per set to do for an underweight guy looking to build muscle mass?
Doing less wieght and more reps helps increase and tone your muscles, but doing more weight and less reps gives you more mass. Mixing it up and sticking to routine can help it look and actually feel like muscle.Im very confused by how many reps per set to do for an underweight guy looking to build muscle mass?
HERES WHAT YOU DO!!!

day 1:

Chest, Triceps, Forearms.

4-6 sets.

First set 20 reps light weight, (to warm up muscle)

second set 15 reps. moderately heavy struggle at 12.

3rd set, 10 reps raise weight.

4th set, keep weight at previous weight from your last set, and 15 reps.

5th set, 10 reps same weight.

6th set, 15 reps.

1 minute rest inbetween sets.



THE REASON you do reps and Less reps is so you can tear the smaller muscles by doing more reps and then get them bigger by doing less reps.



Day 2; Back, biceps.

Same amount of reps and sets, (same format)



Day 3; Shoulders.

Same amount of reps and sets (same format)



Day 4; Legs

Same amount of reps and sets. (same format)



Day 5; Rest



Day 6: Rest



Day 7: repeat day 1.

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