"The backpack is in front of the desk."
Translation:배낭이 책상 앞에 있어요.
If by suffix you mean particle, there is none when you add a preposition.
Your sentence means "the desk is in front of the backpack" and 이 should be put with 책상 .
Okay that was a mistake when I was typing my question. I was using the word-select option for the actual response.