As a result of adding a CSV file, press the Export button and choose vCard format from the drop-down menu.In this folder, select the CSV files and import them. Select Import -> CSV Comma Separated Values from the Contacts pane.Type contacts into the Windows Search box.To save the contacts in CSV format, click OK & Finish.Select the Contacts folder, then Browse a location to save the file.
From File menu, Select File -> Open & Import – > Import/Export. Here is the manual method or the common method to backup Outlook contacts to iCloud on Windows OS. How to Import Contact from Outlook to iCloud on Windows?
