You cannot scream in outer space for many reasons. Firstly, you need to be able to breathe in air to be able to scream.
Sound is made when air in your larynx goes through what is popularly known as "your voice box", making sound. That sound can be your regular speaking voice, a whisper, or even a scream.
Secondly, sound travels through gasses, such as the air we breathe. Without any gas, the sound cannot travel past your larynx. Since Outer Space is a vacuum with no air (or such a small percentage, its practically 0%), sound cannot travel from your larynx to another person's ear.