Here's what works for me.

Using office manager, create a backup into the folder C:/ConversionData. That should produce Zip folders pertaining to the backed up clients and one CLNTBKUP.zip folder. 

After that, the TDexport.exe never works for me. Instead you go into you /WFX32/Client and grab all the files pertaining to the backed up clients and paste them into your ConversionData folder.

This includes the client U files, B files, H files and C files. Ensure you keep the files in their proper folders 21I, 20I, 21P, etc. Also look for the pertinent files in HISTORY copy those over as well.

Last thing, make a text file and name it conversion.exp.

After you do all these steps, the lacerte conversion wizard should see your files