[Koha] Backup and migrate Koha from one server to another

I am migrating Koha from one server to another. On the old server, I run # koha-dump library I got two dump files for the database and the configuration On the new server, I run # koha-restore sqldumpfile configdumpfile I see that on the new server, I have the new instance folders in the /etc/koha/sites and also the new databases. However, when I access http://library-admin.usj.edu.mo:8080, I was asked to lead to the " Welcome to the Koha web installer" web page. I thought I should be displayed with the admin login page to access my old Koha server contents. Can anyone tell me what has been done wrong here? Or what is the appropriate procedure to move Koha from one server to another? Regards, Kitty