Android: First connect your phone to a computer via USB cable, you will need an application such as Android file transfer installed on your computer. Now with My Computer opened, go to the SD card and copy the files you need to backup. Once completed you can unplug your android phone.
iPhone: Connect your device to your Mac or PC. If using Mac OS Catalina 10.15, open Finder, if you are using Mac OS Mojave 10.14 or earlier, or on a PC, open iTunes. Locate your iPhone on your Mac or PC, you can choose to backup to iCloud or your Mac or PC. Click the blue Back UP Now button. Once complete, click the eject symbol by your phone to eject.