Flash drive formatting warning message

[annietravels]

Need to do factory backup of new Del laptop onto 16 gb sub flash drive, get warning message saying "all the partitions & data present will be lost" did not proceed as worried the message is referring to data & files on laptop or is it referring to Usb ( brand new )

 

[annietravels]

Sorry not sub flash drive it's 16gb flash drive and I'm trying to back up "dell backup & recovery" System Backup. As you probably realise by my question not too computer savvy