Flashing question mark folder on boot up

I was gifted a Mac Mini model A1347, I believe its a late 2014 model. 2.6GHz Intel Core i5 with 8gb of LPDDR3. I was told the Mac has only been used a handful of times since its been purchased. When I tried to boot, I got a flashing ? folder, and after research I've found that this is most likely because the mac no longer has a working operating system. I'm not familiar with Apple products at all, so I'm wondering what my next course of action should be. Attempt to boot from a USB with a current OS? Would Geek Squad possibly still work on it even though its outdated? Thanks!