How to update iPod touch 5th gen to version 10? it already say "version up to date" in version 9.3.5

Other than the new-ish iPod Touch 6th generation, none of the older iPod Touch models are capable of upgrading to iOS 10.

The 5th gen iPod Touch is a, now, 5 year old device with 5 year old specs and technology.

iOS 9.3.5 is the farthest iOS version your iPod Touch can go.

It will still receive app updates relevant to indivudual apps that still support iOS 9.3.5 and earlier.

iOS 9.3.5 is the last version that the iPod touch 5th Generation can operate. If you want to run iOS 10 you'll need to get an iPod Touch 6th generation, or one of the newer iPhone or iPad models.

You can’t. iOS 10 requires an A6 or better CPU.

(151020)