Step 1: Open Outlook and navigate to File >> Open & Export >> Import/Export
Step 2: In the Import and Export Wizard window, select Export to a file and click Next
Step 3: In the Export to a File window, select Outlook Data File (.pst) and click Next
Step 4: In the Export Outlook Data file window, select the folder from which the data will be exported
Step 5: Click on Filter button, select More choices.
Step 6: Check the Only items that are checkbox and select unread.
Step 7: Click Next, OK and then Finish.