Backing up files without access to desktop- SMART error

I cannot access my desktop because my laptop won’t load enough to reboot. When I try to reinstall the operating system I’m getting the SMART error. I know this means my hard drive will die at any given moment now, and I want to back everything up. But I can’t? I don’t know how to back up files without getting to my desktop. Will Apple support be able to help me at the store or is this a lost hope?