Would i play defensive lineman? Offensive? Linebacker? First year, middle school football.?

I am 5 foot 5 and 140 lbs. That is a mix of fat and muscle, but it is not holding me back. I am strong, but only so so in speed. I have good hands. So, i dont know about any running positions, but again, i am strong and think i will be able to hit pretty hard. I am not sure of what size coaches look for in middle school football for the different positions. I want to know what to practice for. I will be in eigth grade, and want to get there and be partially good.