Depending on if your mobile device supports it, you could use an OTG attachment and let your mobile device do all the file transfers. Use a USB card reader to put the files onto your phone, unplug, and then put in a flash drive to transfer the files back onto.
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But yes, you will have to buy an OTG cable/adapter, USB card reader, and flash drive.
Depending on if your mobile device supports it, you could use an OTG attachment and let your mobile device do all the file transfers. Use a USB card reader to put the files onto your phone, unplug, and then put in a flash drive to transfer the files back onto.