Q: i have an old ipod touch and app store wont appear

Check for a restriction in Settings > General > Restrictions > Installing Apps

Home Screen: Missing App Store, FaceTime, iTunes or Other Icon

You need at least iOS 2 for the App store. Go to Settings>General>About>Version. If you do not have iOS 2 or greater you hvae a 1G (original iPod) and those can go as high as 3.1.3 that you get here

Purchasing iOS 3.1 Software Update for iPod touch (1st generation)       

https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/touchLegacyLandingPage

To more easily find compatible apps (mose apps now require a higher iOS version/later model iPod):

iOSSearch - search the iTunes store for compatible apps.

Apple Club - filter apps by iOS version.