Q: tried to restore a drive and picked the wrong one. My main drive Macintosh HD is gone. how do i get it back?

i have mac air with El capitan. was trying to repair the constant start up in safe mode.

by accident picked wrong drive to restore and picked the OX System drive whatever it might with tiny memory of 1.33 GB.

now Macintosh HD is gone. cant find it and on my external back up drive the back ups are not showing. i think becuase my mac is looking for the drive to restore it to but is gone. ahh... what do i do??