Q: how do you find latest version of itunes? hooked up new ipod says must download version 10.6.3 from store but not finding

How do you go to itunes store to update the version of itunes you have?  Got new ipod and it will not let me sync it so it works. When I hook it up to itunes it tells me to go to itunes to download 10.6.3 version.  I can't find anywhere versions of itunes to do this.  can you help?