Translations:GRUB/Restore the GRUB Bootloader/5/en
From Manjaro
Identify partitions
To identify your partitions and their designated use you need to run a partition manager. Depending on environment there is various tools. GTK based ISO offers GpartEd, QT based ISO offers KParted and common to all is the CLI tools.
user $ lsblk -o PATH,PTTYPE,PARTTYPE,FSTYPE,PARTTYPENAME
More comprehensive information can be found using fdisk (requires superuser) and you can limit the probed device e.g. /dev/sda or /dev/nvme0n1
user $ sudo fdisk -l /dev/sda
The clues to look for is mbr vs. gpt and the presence of a small partition - usually the first - formatted with the vfat filesystem followed by a larger partition formatted as ext4.