Enemy Respawn Help

Hi,

I am doing a space invader type game and wondering how to respawn all the enemies when the last one has been destroyed.

I have 3 rows of 10 enemies (all of the same sprite). When the last one has been destroyed i need all 30 to be respawned again.

Whats the best way to do this.

Thanks

EDIT - Think i have sorted it. Merely just Restart Layout..

Just had to alter my instance variable to global so i didnt lose my count in that variable.