[Beginner]Images and Retina Display

Hello,

First I am not a designer at all and therefore really struggle with this kind of question. I read this http://www.macrumors.com/2014/05/14/3x-iphone-6-transition/ but could not help me further.

I understand that because of retina display I have to add all my images in a different format to support IPhone devices. So if I have an image with size of (50X50) I need to add it three times for iPhone
· Normal (50 X 50)
· @2x - Retina (100 X 100)
· @3x - Retina HD (150 X 150)
Now my challenge: I designed my app for an iPad. What does this mean for the images. Do I still need to add the graphic three times in different sizes ?

Thank you for your answers,
Tim