Need to transfer data from childhood account to new account.

i'm sorry nothing could be transferred between accounts. If you haven't used the account in 6 to 7 years, it's quite possible that it has been deleted since if there's no activity five years is typically the limit

please keep in mind any Microsoft feature like Skype, Outlook, etc. would do to keep the account open

You can start the process here, so I am skeptical of success after all this time. Best of luck

https://support.microsoft.com/en-us/account-billing/help-with-the-microsoft-account-recovery-form-b19c02d1-a782-dee6-93c3-dc8113b20c42

Hello, so you mean you create a new account and want to transfer the contenue from the old account to the new one?

Unfortunately is not possible. Any sort of data and content that is downloaded/saved on one gamertag is not transferable to another account.

I know I'm not getting the account back, but surely there must be a way to just transfer the data to my new Microsoft account right? The account itself is not what matters, it's the data (which includes the account I've had for a decade). Is it possible to get that data transferred to my new account?

I did not verify my emali on that activision account and Can i Make a new Microsoft account and transfer data From my old Microsoft account to my new account?

A heads up, even with using the data transfer cable you will need to log into the account on the new xbox and do a license transfer and "redownload the data", truthfully it just update what xbox has the rights to play that content.