How to Mount an External USB Drive in Debian 10 Linux

If the option to automatically mount USB devices has been disabled, or if the device has been unmounted, you can manually mount it by using terminal:

Type fdisk -l and press “Enter” to find the device name of your USB drive. It will look similar to “/dev/sdb/.”
Type the command file -s /dev/sdb and press “Enter” to find the file system of the drive, replacing “/dev/sdb” with the correct device name. The FAT32 file system will be listed after “OEM-ID” as “mkdosfs” and the NTFS file system will be listed as “NTFS.” If “EXT4” is listed in the results of the command, the drive uses the Linux EXT4 file system.
Create a mount point for your device by typing mkdir /mnt/external and pressing “Enter” A mount point is simply a directory where the files from your drive will be linked so that you can locate them. The directory name, “external” in the example, can be any name that you would like, just avoid using spaces and remember that the name is case-sensitive.
Mount the device with the mount -t vfat /dev/sdb /mnt/external command, followed by the “Enter” key. Replace “sdb” and “external” with the appropriate device and directory. Replace “vfat” (used for FAT32 file systems) with “ntfs-3g” for NTFS file systems or “ext4” for EXT4 file systems. To unmount the drive when you are finished, type umount /dev/sdb and press “Enter”