Upgrade from D7 to D8

Hi  I want to upgrade my drupal csm from a FTP , already download D8 and put mi web in maintence mode.

I cant understand where I replace the core folder or Vendor folder. 

This is my files on ftp. 

ftp files  folder

tmpsite
tmp
public_html
oxdata
mail
logos
etc
.trash

Public_html files

thumbnails
themes
sites
scripts
profiles
new_img
modules
misc
includes
img
cgi-bin
video

Drupal version: 


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