I don't know if the latest DXbase will import DXbase 4.0 files or not.
I helped a guy a couple of years ago export his DXbase DOS log to DX4WIN. You have to export your log to an SDF file, which is Space Delimited.
From there you can bring it into Excel to manipulate as needed. KH2D has an ascii to ADIF converter at http://kh2d.net/software/asc2adif.cfm
. I think there are other ADIF converters as well.