Hey!
It is important to know that directly moving the data and subscription of one tenant (GoDaddy in this example) to another (Microsoft) is not feasible. You may manually remove the domain from the Office 365 tenant in GoDaddy, cancel the Office 365 subscription, then purchase an Office 365 subscription in Microsoft, and add the domain into this Office 365 subscription.
Here is how you get started:
1. If you are using the Outlook client now, exporting and importing the pst files may be a good choice.
Here are two articles for reference:
Export mail, contacts and calendars to an Outlook .PST file.
https://support.office.com/en-us/article/Export-or-backup-email-contacts-and-calendar-to-an-Outlook-...Import email, contacts, and calendar from an Outlook .pst file
https://support.office.com/en-us/article/Import-email-contacts-and-calendar-from-an-Outlook-pst-file...Here are the steps to change your subscription from GoDaddy to Microsoft:
1. Back up your emails from GoDaddy.
2. Remove your custom domain from the Essentials plan.
3. Cancel (delete) your Office 365 plan in GoDaddy.
4. Purchase an Office 365 plan from Microsoft directly.
5. Add and verify your domain in Office 365.
6. Import your emails to Microsoft with pst files.
7. All done!
