How to add small text (Perfect ... Great ! ...) when enemy dies

Hi there,
I'm new at unity3d and game developement , I made a simple 2d game , now , I wanna add some popup text when you kill many enemies in a short time ; for example ; you kill 5 ,in the 6th enemy you kill , a small text will appear and say : Perfect . at the 7th , it will say : Great ! ...
I don't know how to do that , please help
thanks

 

use ui canvas and text and put counter in update func.

 

thank you so much

 

no worries