>>106846836
I don't use Ubuntu Exactly but there should be just one file explorer, Nautilus. The "Disks App" is probably a disk management (Gparted?) or volume inspection utility which is the equivalent of diskmgmt.msc on windows, a separate utility from explorer.exe
The file manager would also list the disks though and most file managers, including Nautilus, Dolphin and Thunar will support the basic operations with Disk (encryption/formatting), that windows does through the context menu.