You should use a 301-Redirect, which is a server response that claims google that this site just moved to another domain and isntisn't just temporarytemporarily unavailable or something.
On top of that you should use the "canonical url" meta tag for google, to consolidate duplicatedduplicate pages/content.
Here you can find more about that: https://support.google.com/webmasters/answer/139066?hl=en
Hope this helps ;)