Export Calendar from Gmail to .ical file
- Sign in Gmail
Username : UID
Password: PIN
- Export Calendar Open Google Calendar.In the top right, click Settings
Settings.
Import Calendar (.ical) to M365
- Sign in to M365 Outlook (https://outlook.office.com)
- Create Blank Calendar and Import .ical file
Create Blank Calendar
Go to Calendar > At the left panel of the page, select 
Select “Add Calendar”
Select “Create blank calendar”, name the calendar and select Save
New Calendar will show at Calendars List
Import .ical to Blank Calendar
Select “Add Calendar”
Select “Upload from file”
Browse and select .ics file
Select the new created blank calendar and click Import
Success Message will show at buttom.
Event will add to Calendar
Please repeat above step to add all exported calendar to M365.