When removing an existing partition even reformatting one your last chance is a data recovery program if not a professional data recovery service to see what little can be undeleted. A few programs like Active Undelete, Recuva, or another might see some of your files rescued.
One tip advised when first getting an external is seen at drive manufacturer's support sites regarding first seeing the factory Fat32 partition converted or reformatted to NTFS for Windows only users before starting to place files on them. A download is available for replacing the original program on the factory partition.
What make of drive is it? WD will first require the serial number of the drive itself before allowing you to download the zip file containing the replacement program. At Seagate's site you can readily download that. Once saved to a folder you simply unpack the files in the zip onto the external drive.