ChemDraw: Transformation of Previously Prepared Marvin Sketches to Chemdraw.

How do I transform Marvin Sketches to ChemDraw files?

If you have saved them as .mrv files you can resave them as .cdx and open them in ChemDraw.
If you have a lot of files, Marvin has a tool that can convert them in bulk to .cdx, Molconvert. 

Here is the link to the Chemaxon list,
https://docs.chemaxon.com/display/docs/molconvert.md