If you don't renew your subscription during the grace period, your account will be deactivated and all your data will be deleted. This means you'll lose access to all your files, emails, and other data that's stored in Office 365.
If you don't renew your Microsoft 365 subscription, you will lose access to all the Microsoft 365 apps including OneDrive storage. You back up your files from OneDrive. In the meantime, you can use Office Online for free in your web browser.