Technical documentation including document use cases and user stories for an app

Looking for someone that can document use cases and user stories of an already built app in excel. It is expected that the person can breakdown the features and structure of the built app in user stories and use cases and hence have product management knowledge and have previously worked with use cases and user stories. It is also expected that you catalogise and attach screen shots (from the app) to each use case for reference.

Experience:
- Product Management
- Use cases and user stories
- Product back-log
- Product roadmap