To be clear - are you asking for a way to “migrate user settings | preferences from KDE to gnome” ??
If that’s true, “good luck” is the answer (my personal opinion).
Your best option for this situation is to simply -start from scratch- and install Leap 16 with gnome as a fresh install (alongside your current KDE install or wipe it away, though I’d keep a /home backup). Then make whatever DE (gnome) alterations you want, then install all your [required] software and manually migrate all your login accounts as needed.
Here’s what one person did, but I’m confident none of their DE settings and accounts were migrated properly: