How about I snatch my things from my 3 yo brother and yell?
Are you serious? Why do you want to snatch your things from your 3 year old brother?
Because he was looking through my stuff
While it is wrong for your brother to take your things, you shouldn't snatch and yell at him. He is too little and doesn't understand, it would be better to try to explain it to him.
He can understand I'm his big brother and I can teach him this lesson. The most important thing here is that I want my stuff back and to teach him a lesson.
It is good for him to learn not to take things that are not his and as his big brother, you are a good person to teach him this but yelling is not good. Teach him more gently so he does it because he understands not because he is scared.