Enemies in a row

So I just started coding in unity and now I’ve made a simple space shooter-ish game where an enemy comes from right to left. After the enemy exits the screen he resets and comes back from the right in a random y position. How do I make it so that 3 or so enemies come in a row?

Its just a matter of making a function that checks if the enemy has gone off the screen and then spawns a number of the same prefab in the position that you want them to.

this might help