That app wasn't created by Microsoft, so Microsoft can't say for sure whether it's safe.
Apps sold on Microsoft Store have to meet certain requirements for safety. Nevertheless, Microsoft doesn't have access to the source code so they can't vouch for its safety.
I advise you to check carefully as you would with anything else you buy. What do reviewers say? How often is the app updated? When was the last update? The more knowledge about an app that you have, the more confident you can feel in your decision.