First of, you need to download seafile to be able to use the seaf-fsck tool. If you are on a windows computer you can also use ubuntu via wsl.
Download & extract seafile
sudo apt -y install wget
export VER="7.1.3"
wget https://download.seadrive.org/seafile-server_${VER}_x86-64.tar.gz
sudo tar -xvf seafile-server_${VER}_x86-64.tar.gz -C /srv
sudo mv /srv/seafile-server-${VER} /srv/seafile