To transfer Google Takeout data to a hard drive using the MacSonik MBOX Converter, first export your Gmail data from Google Takeout in MBOX format and unzip the downloaded file. Then, install and open the MacSonik MBOX Converter on your Mac, add the extracted MBOX files, and choose an output format such as PDF, PST, or EML. Set your external hard drive as the destination location and start the conversion. The tool quickly converts and saves your emails to the drive while preserving folder hierarchy, attachments, and metadata. With features like bulk conversion, mail filters, duplicate removal, and local processing for data security, the MacSonik MBOX Converter provides an efficient and reliable way to back up Google Takeout data on a hard drive.