Is there an equivalent program to the windows explorer for Ubuntu? [duplicate]
I'd recommend Thunar.
You can get the tree view in the side panel by just setting this mode in View -> Side Pane -> Tree:
I'm pretty sure Nautilus can show a folder tree in it's side pane, it's switchable between the "Places" or a tree (maybe other options too). https://askubuntu.com/a/339138 [May even be a duplicate Q]
As can Thunar (XFCE file manager)