This will only work between these two figures or between their male counterparts. It will not work between any previous figures, or between these and previous figures.
Here's the YouTube video.
For this tutorial you need:
Genesis 3 Female from Daz3d.com.
Genesis 8 Female from Daz3d.com.
An item of clothing for one of them that you want to convert to the other one.
Scene Tab and Parameters Tab in Daz Studio 4.9+. If you lack a tab, you can add it using Window--Panes (Tabs) and clicking the one that you need.
THE CONTENT MANAGEMENT/SMART CONTENT HAS TO BE INSTALLED AND WORKING TO USE THIS METHOD. IF YOU CANNOT SEE THE COMPATIBILITY BASE IT IS NOT ON. CHECK THE BOTTOM OF THE SMART CONTENT TAB FOR A "START CMS" BUTTON. IN YOUR DAZ INSTALL MANAGER IT'S CALLED POSTGRES SQL CMS OR SO