Changing FTP info

I just tried to fp into a site but it failed. I have no wp-config.php file to get the name and pass.A dozen sites all failed and no backup on my machine of config.

So I figured I’d set up a new name and pass for each db. But I’d need to change the config file on each.

IF I change the info in my host admin, I’m worried i can’t get into the site admin.

I’m asking for the steps to take to add a user/pass for each db but stlll be able to login. If I have to change admin login , how?

How do I change config file for each site?

I want to ftp in first, copy each site to this machine, then proceed without losing my content