Use ‘lsblk’ to determine which drive is the SD card.
To copy an iso or img file to the SD card, use:
sudo dd bs=4M if=2021-10-30-raspios-bullseye-armhf-full.img of=/dev/sdd status=progress oflag=sync
To backup an SD card to a file, use:
sudo dd bs=4M if=/dev/sdd of=sd_backup.iso status=progress oflag=sync