How do I retrieve files from Back up sync?

I hate looking stupid but I usually have little say over the matter. I've wiped my hard drive clean but in a moment of rare mental clarity I backed everything up into 'Back up and Sync.' 
 
How do I retrieve these irreplaceable gems of wit and wisdom???
 
It's clear that I can click and drag but that seems to remove said file from back up and sync and then it only lives on my hard drive?
 
Even I understand it would be better to have it in both places.                      
 
                                             
                                                                          Thanks much
                                                           Neoluddite, aka the last human without a cell phone