I made a backup of my (very) old WP installation and then deleted the files that are recommended in the install help files.
When I uploaded the new WP files I was constantly asked to overwrite older files, which I did.
Now I can see the WP blog with my header and footer. All the posts seem to be there.
But there is no admin to complete the upgrade. All I see is:
Sorry, but you are looking for something that isn't here.
Can any help with sorting this problem please? I have very basic tech skills, so you will need to describe ABC what I need to do.