Data transfer add ons

That's what I thought but when I try and reinstall them on the new one it dosnt show and i need to buy them which i know I had those dlc

Unless they were bought on a different account, that should work. Purchases aren't tied to the console.

That didn't work as the add ons where bought on my old xbox and when I tried to transfer that didn't work

Check your account at http://account.microsoft.com to see if it shows the purchases there. If not, then they were purchased on a different account and you would need that account.

For the games you have add-ons for, highlight them in Games and Apps and press the menu button on your controller and go to manage games. It should show a list of everything you own for the game and you can install them from there. Or look them up in the store and reinstall them from there.