Super utile, quand on a des fichiers à mettre sur le nextcloud alors qu'il sont déjà sur le serveur (exemple : gros fichier uploadé avec scp)

Find Nextclouds data directory. I think by default it is somewhere in the document root of your webserver, so in /var/www/html. Mine is different because I run a docker container so I can't tell you exactly. The folder you are looking for is called data.
In the data folder there are folders for each user. Go into USERNAME/files/ and copy or move the data here. Of course replace USERNAME with the actual name of the user :) This is by the way the place where all your actual data lies. The metadata is stored in the database.
Now the data is in the right place but Nextcloud doesn't know about it yet. You have to scan the folder to create entries in the database. To do that you will use the occ command: sudo -u www-data php occ files:scan --path USERNAME/files/FOLDERNAME You can specify a path to avoid scanning all your data which can take a long time. However for your 120GB that shouldn't be a problem so you could also use sudo -u www-data php occ files:scan --all
Now just wait for the operation to complete and all your data should appear in the Nextcloud interface.