Connect to iTunes on the computer you usually Sync with and “ Check for Updates “...
If an Update Appears Install it... if not... you are up to date for your particular Device...
See the Using iTunes Section Here...
If yours is a 2nd Gen... iOS 4.2.1 is as far as it can go.
Identify iPod Models
4. iPad Support
a. Updating Your iOS to Version 6.0.x from iOS 5
Tap Settings > General > Software Update
If an update is available there will be an active Update button. If you are current,
then you will see a gray screen with a message saying your are up to date.
b. If you are still using iOS 4 — Updating your device to iOS 5 or later.
c. Resolving update problems