Upgrade of my OS X Yosemite 10.10.5 on my iMac (21.5 inch, late 2013)
Trying to upgrade my OS but not sure which is best (or available)?
Mountain Lion is available for purchase, but from the site High Sierra would be the next step! This does not seem available however.
Any assistance or guidance would be much appreciated.
iMac 21.5″, OS X 10.10