Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Open Word.
Go to File - Account, on that window, you will see the Email address of the Microsoft account you previously used for the Microsoft 365 subscription.
If you have taken out a new subscription on a different Microsoft account, there is no native process to switch everything over to the new Microsoft account and all your files would be synced to the OneDrive of your previous Microsoft account.
The only way to correctly resolve this would be to use the steps provided on this link to cancel the new subscription to get a refund, then take out a new subscription on the correct Microsoft account.
You can check your eligibility for a refund using the steps on this link.