Actually, the easiest way to backup FTP to Google Drive is to use a cloud backup tool or services, some multicloud stuff such as MultCloud Get here one Month free or here https://www.multcloud.com/partners/covid19/remote-work-giveaway-5566.html
You can also try CBackupper
You can easily connect FTP and Google Drive on one interface, and then, create a backup task to back entire FTP or some of the files on it to Google Drive directly and quickly.
Still you said 
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