my iphone will not show in itunes

You've posted in the iTunes for Mac forum. The Microsoft Store is for Windows computers. Are you running WIndows 10?

Try this from About the 'Trust This Computer' alert on your iPhone, iPad, or iPod touch - Apple Support.

Change your settings for trusted computers

Your device remembers the computers you've chosen to trust.

If you don't want to trust a computer or other device anymore, change the privacy settings on your iPhone, iPad or iPod touch. Go to Settings > General > Reset > Reset Location & Privacy. Now when you connect to formerly trusted computers, the Trust alert will ask you whether you trust that computer. 

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