I tried to reinstall Composer again, I choose the 'wamp64 php 7.0.0' option in the installation, I switch the WAMPSERVER works with PHP 7.0.0 and use again the command: "composer create-project flarum/flarum . --stability=beta" to get the files of the Flarum system.
Now, it's take lots of time before I used that, And I got the "vendor" directory with many sub directories and the autoload.php file, It's works now!
Thanks for help.