A script is available in rescue mode for mounting the partitions of the disks. It only requires to type the following:
sudo mountall.sh
The partitions are then available in the directory /mnt.
A directory corresponding to each partition has been created.
This means you find the partition /dev/sda1 mounted in /mnt/sda1.
You may see some errors when running the script, as it tries to mount the SWAP partition.
This is normal and you can simply ignore it.