First of all, download Thunderbird Export Tool and launch perfectly on your computer desktop. When it gets launched, the screenshot will be appeared as:
Here, you will get two options to load Thunderbird profiles :
Convert Default Configured Thunderbird Mailboxes
Let me select other Thunderbird Pofiles/mailboxes saved separately
If you choose Default Thunderbird profile and click on Next, the software will then automatically load Thunderbird profile data from its default location.
If, you want to manually select Thunderbird profiles, then choose the second option and click on Next
Now, you will get two options to load Thunderbird profiles manually, File Mode & Folder Mode. Select Thundberbird user profiles using any of the provided options and then, click on Next.
After selecting and adding Thunderbird mailboxes, software will show the preview of all selected Thunderbird emails. And then, hit on the Next.
Now choose the output option in which you need to export Thunderbird profiles or mailboxes. Then click on the Next.