The auto-complete list for Outlook 2010 and above is stored in .dat files in the RoamCache folder under the Local AppData folders. You can access this folder by typing or pasting the following command into the address bar of Windows Explorer and pressing enter.
%localappdata%MicrosoftOutlookRoamCache
You can use a utility to extract the addresses from the auto-complete stream and insert them into the new auto-complete stream. Or you could rename the .dat file with the name of the new .dat file, however, because the auto-complete tends to corrupt easily, make sure you export the addresses to a CSV file first, otherwise you might lose the addresses.