If you saved the entire folder a song was in, you should be able to drag and drop a copy of the folder back in under Songs (or wherever you save them) and it should work. ALWAYS save the entire song's folder, NEVER just individual files, because hidden files are in there about the song's creation (plugins, etc.).
And always use iCloud Drive on Mac, or Google Drive's Backup & Sync on PCs to keep backups of your work offline.
$2.99 for 200GB a month on either service. 100GB a year for $19.99 on Google and $29.99 a year for 200GB on Google. I pay $1.99 a month for 100GB on iCloud. Unfortunately, Apple doesn't have an annual rate, that I'm aware of.
Since you said you're a newbie to S1, I'd suggest watching a video or 2 about song creation in S1 under the Tutorials from your MyProducts page. At least one of the guys goes into detail about how and where the song files are saved and covers what I can't remember off the top of this aged noggin. Pretty sure that David Vignola's video covers this quite well. He makes sure you understand how to backup ALL of a song's files.