Hello Joyce, this can be done either way....cost & aesthetics will be the determining factors.

Dry stacked stone walls cost more as they require greater amounts of stone in addition to more labour, only high end homes still build this way in todays residential construction world. Mortaring thinner stones (veneer) over concrete blocks is very common & usually saves money on labour costs + less structural considerations due to decreased weight loads. This method is used almost exclusively for interior fireplaces, walls etc.. In your circumstance, keep in mind that dependant on where you live geographically, you'll need a foundation of some sort that goes below the frost line for your region to avoid future frost heaving. Good luck !

That's very helpful... thank you!!