Hi Natasha Kiew, thanks for adding more details to the question.
Now I guess, I know what you want to do.
You can try this with PowerShell:
Set-MailboxCalendarFolder mailbox:\Calendar -PublishEnabled $true
With this, the calendar of the mailbox is public on the internet.
You can retrieve the ics URL via:
Get-MailboxCalendarFolder sharednew:\Calendar | select PublishedCalendarUrl,PublishedICalUrl
OR
check out the feature via GUI.
"Share your calender"
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