Check with your administrator if you're using a work device. Microsoft Store may have been turned off.
Still can't find Microsoft Store? Send us feedback. In the search box on the taskbar, search for Feedback Hub and open the feedback app. Make sure you're signed in with your Microsoft account. Type a description of your situation and then select Add new Feedback, or upvote the existing options that pop up that are similar to your situation.
If you've found Microsoft Store and it isn't working properly, see: