Follow the steps to understand the Thunderbird export wizard
Step 1: Install and Run Thunderbird Export Wizard
Step 2: Browse the files/folders to load in the application panel.
Step 3: Select the folders & it's subfolders by checking/unchecking them.
Step 4: Setup Export Thunderbird Conversion options.
Step 5: Choose the destination path to save the resultant.
Step 6: Click on the Next button to start the conversion process.
Step 7: Click on the OK button to Confirm & Exit from the tool.
Step 8: Directly access the resultant files from the destination path.