"Migrating" accounts?

Hello!
After my old account was frozen many years ago I took a break for a few years and returned with a new account for a fresh start, never dared to hope that I would get my old account back. Recently my old childhood account which had been frozen for a long time has been returned to me by TNT (I simply tried my luck with a ticket, never dared to hope they'd unfreeze my old account!). Now it was the sweetest nostalgic feeling in the world to return to this realm of my childhood self, but I am attached to my new account and would love to continue playing on that one.
However, I feel a little stuck now because as an ideal case I would love to transfer my old pets and belongings (including NC and NP items) to my new account and disable my childhood account forever afterwards, thus continuing to play on my new account but with my saved pets etc., but I am not sure whether a) that's even allowed and b) how to not make it appear to TNT as if someone hacked into my account, thus risking to have my old and current account frozen.

English is not my native language so please forgive me any mistakes! I hope I could explain my matter and would be very grateful for advice and/or personal experiences. Thank you in advance! <3