How to Retrieve programming assignment file?

I started doing my W3 programming assignment. I need to retrieve that original file, but it showing saved file. I am unable to that . Hoe to do that?

Coursera Help Center.

This is the link guidance to solve problems and reset the notebook to its original state.

sorry for this i had not found any info there .I tried all the things. Can you plz explain me step by step procedure please