Just connect it to your computer which you back up your iPod on.
Is it yours? The reason I ask is that it locks everyone out if you don't enter the correct password. So if its yours you should know the password and should be able to unlock it. If you have forgotten the password you can get it to open by connecting to the I tunes version that it is synced to. It will recognize the computer as belonging to the owner since it is the one that is used with it. That is why it is asking. If it is stolen then the best thing you can do is return it to the owner and maybe hope to get a finders reward.