You can follow below steps to convert Thunderbird data to Outlook.
- Open Thunderbird
- Select which messages you would want to export to Outlook
- After selection, right-click and select “Forward as Attachments”
- Open Outlook and click Send and Receive
- Now open the email (that contains the email attachments) and move this window down on the screen so you can see the main inbox area in Outlook.
- Select all of the attachments in the message and drag them into Outlook Inbox folder.