Microsoft App Store issue

So, I went to log into the Microsoft App Store and download windows defender and it asked for my pin and it worked but then it asked for a code that it sent to an email I didn’t recognize. It was like S****@163.com and I know that email is not mine. I’m not sure what to do. I know a whole back I had malware on my pc and I cleaned it out but it seems there is leftover issues. Long story short I now can’t download anything off the App Store and want to figure out how to get that email off. 

please and thank you for any help.