Old gamer coming back, confused about transferring account, please help :)

So I played back in 2009 until like 2011? Then stopped and about two years ago played again, then stopped. Now I picked it back up just because I missed Ghost Mode, now I can't log in. Was told EU and NA merged and had to now transfer account? Could anyone help me understand this more and how I would be able to transfer my old account? THANKS SO MUCH!


Account username 98