How do I get all my Mac mini Contacts and Calendar events to sync with my iCloud?

Short Answer: you don't.

Long Answer, you would need to move each contact and each calendar entry from Outlook to the iCloud Calendar and Contacts group manually. There is no automatic transfer to iCloud.

With that said, your Outlook Calendar and Contacts should be able to accessed on all devices where you have added

your Outlook email account, for Contacts and Calendar in Settings without the need to move them to iCloud.

On a Mac, in the Apple Calendar app, you can click on the Calendar menu at the top, Accounts, Add Account, select Microsoft Exchange, and add your accounts details.

Same thing for Contacts, though once you add it for one, it should appear for the other too.