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There are two parts to your question.
1) port your game built from Unity to UWP
For this question, you might need to ask in the Unity forum.
2) upload your game to the store
There are no video tutorials about this. But there are complete documents about the whole process here: Publish Windows apps and games. This is the overview of the process for publishing your app or game to the store. You could go through these documents to learn about how to publish your app and game. You should get started with opening a developer account.
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