You can see the M365 usage with the following method:

Procedures:

• For Outlook: Please visit https://support.microsoft.com/en-us/office/mailbox-storage-limits-in-outlook-f170fe90-b859-4034-bcda-e186fc6a26f5.
• For OneDrive: Please visit https://support.microsoft.com/en-us/office/manage-your-onedrive-for-work-or-school-storage-31519161-059c-4764-b6f8-f5cd29f7fe68.