need help with a script

My name is Robert rousan i am working on a simple break out game to get me started with unity what i need help with is when the ball drops past the paddle it goes off screen i need help with respwaning it at a set position thanks also im doing this in c sharp and i have lookedf around allready

Make a script and attach it to your ball object and write

Function Update()
{
  If(transform.y<20)
    {
    Transform.y = 50;
   }
}

This code will check all the time to see if your object has fallen below a y position of 20, if that is true it will put it back to 50, change these values to fit what you want.