1. It just hit me that yours was not a self hosted site. You are hosting at wordpress.com. I have never used them as host.
OR
your have a self hosted site but got your domain name wrong. My guess is that when you added domain name as a sub-domain or an addon domain it would be
wordpress.mydomain.com … where wordpress is a subdirectory under mydomain directory.
and not https://mydomain.wordpress.com
If yours is a self hosted site, meaning your are not using WordPress to host your site:-
2. When you install WordPress, especially the one click installations, you will need to specify the database name. Give it name. Many host will use your hosting account username as your database username and your hosting account password as you database password. If you installation procedure asks you for them you can use your account username and password or give a different password.
3. When you said “I then downloaded WordPress and used an ftp program to copy the files into a site folder called wordpress.”. This may give you additional problems.
Go through the full fresh installation, don’t copy any files. I believe you have database somewhere else, right? It looks like you are either moving site or moving to a sub-domain, right? Are you moving your wordpress site to another domain? or are you creating a new wordpress site? If you are creating a new wordpress site you should be ready to go. It should work like a new installation – empty, blank, fresh and don’t modify your config files.
Be very careful here
please see https://codex.www.ads-software.com/Moving_WordPress for correct procedure.
Options are:-
if you are moving to a subdomain Backup your original database, export using phpmyadmin.
a. Then use phpmyadmin to import the data into your new database or upload the .sql file that was generated by the export and ask your tech support to import it into your new database. There may be a few mods to the tables in the database – I’m not sure.
OR
b. Modify your config.php file to set database name to the old database. This can work if your websites are on the same host account but you may have to edit the database.
please see https://codex.www.ads-software.com/Moving_WordPress for correct procedure.
if it works ok reinstall your plugins and your themes.
I hope this helps and I do hope you can get it running.