How to turn off auto backup feature in Samsung J7 Prime – urgent!

My phone is a Samsung Galaxy J7 prime running Android 7. I’m trying to backup my personal data from the phone to a USB drive via OTG cable.

However, every time I mount the drive, the app files of my phone (com.whatsapp, .nomedia, LOST.DIR, com.symantec.mobilesecurity, etc.) automatically start getting backed up on the drive, which I do not want. How can I turn this feature off and only copy those files onto the drive that I personally select?

Any kind of suggestion or help will be appreciated!