Launching the App Store from iPhone app

1. Launch iTunes on your computer.
2. Search for the item you want to link to.
3. Right-click or control-click on the item’s name in iTunes, then choose “Copy iTunes Store URL” from the pop-up menu.
4. Open the modified URL using an NSURL object and the -[UIApplication openURL] method.

// Watch Technical Q&A QA1629  
// Launching the App Store from an iPhone application  
[[UIApplication sharedApplication] openURL:[NSURL URLWithString:@"http://itunes.apple.com/es/app/lishop/id415119777?mt=8"]];  

For url format see App Store Marketing