Q: I can not open App Store In my iPad mini

Check if you have restriction set in

Settings > General > Restrictions >

     iTunes Store

     Installing Apps

Have you tried:

Can't connect to the iTunes Store

Otherwise what exactly happens when you try to open the app?

Try:

- Reset the iOS device. Nothing will be lost      

Reset iOS device: Hold down the On/Off button and the Home button at the same time for at

least ten seconds, until the Apple logo appears.

- Go to Settings>iTunes and App Store and sign out and sign back in

- Reset all settings                            

Go to Settings > General > Reset and tap Reset All Settings.

All your preferences and settings are reset. Information (such as contacts and calendars) and media (such as songs and videos) aren’t affected.

- Restore from backup. See:                                               

iOS: Back up and restore your iOS device with iCloud or iTunes

- Restore to factory settings/new iOS device.