Here is a complete list of devices whose owners can upgrade to macOS Mojave:
MacBook (early 2015 and newer)Mac OS Mojave received a dark theme, a new Mac App Store, a cool function of Desktop Stacks, an improved Dock and much more.
iMac (end of 2012 and newer)
MacBook Air (mid-2012 and newer)
MacBook Pro (mid-2012 and newer)
Mac Mini (end of 2012 and newer)
Mac Pro (end of 2013, mid-2010, mid-2012)
iMac Pro (2017)