Do I need a registration code for Mixcraft 10?

Nope! In Mixcraft 10, you simply need to log in.  If you haven’t logged in yet, you can do so in Mixcraft by selecting “Login" from Mixcraft 10's Help menu.  This assumes you've created an Acoustica account.  If you haven’t created an account, you can create one here: https://store.acoustica.com/register