Redownload the App Store app
How I can Redownload the App Store in the iphone
You can't. The App Store app isn't one of the built-in apps that can be deleted. If it isn't visible, the usual reason is due to a restriction on purchasing. See: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
If that isn't the cause, try using Search to see if that will locate the App Store app.