Hello Klaus,
I have used Google translator to understand you. Although you don't speak Enlgish it's a good idea to write also the English translation so all other users can understand your question.
Swisslog has a function to import the DOS version database. You only need the LOG.DAT file and also the SWISSPEZ.DXD and all the contents of the NOTES folder. Please read the IMPORT QSO chapter in the Swisslog help or clicking here (in German):
https://www.swisslogforwindows.com/germa...20QSOs.htm
There is also a small chapter with some instructions specifically for importing from the DOS version.
If you need further help, don't hesitate to contact me directly to support@swisslogforwindows.com or posting a message here.