Can’t figure out my FTP address

I created a www.remarpro.com webpage (hosted by 1and1) about 4 years ago. I am just getting back into it, and so have been relearning everything.

Unfortunately, I just installed and activated Bootstrap blocks plug-in (with BusinessWeb Plus theme), and now have the white screen of death. I can’t access my wordpress admin page, and so I can’t deactivate the plug in.

Prior to this, I was trying to figure out how to FTP into my site, so that I could backup the files, etc., but couldn’t figure out my FTP address. I tried https://ftp.tru-6.com, but the username and password that works for the admin control panel of my webpage does not work. I went to the 1and1 webpage, and since my webpage is at www.remarpro.com, there doesn’t seem to be anything at 1and1 that will help me.

Any thoughts? I know I’m probably leaving out too many details… let me know what other details could help.

At wits end… I think my only recourse is FTP’ing into the site and disabling the plug-in. So if I could figure that out, I think I’d be ok. I’ve tried FTP’ing to tru-6.com (and https://ftp.tru-6.com) with CyberDuck and FileZilla and no luck with either.

Thanks!

The page I need help with: [log in to see the link]