Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Start Word. On the main menu bar, click Word, and then click About Microsoft Word. In the dialog box, you should be able to tell which account (e-mail address) stores the subscription license for your Microsoft Office product.
Note that if you purchased a subscription from Apple, presumably via the App Store, you will have to go to the App Store to find subscription details.