dsf to ai conversion is a curious case of export of old Micrografx Designer files to Adobe Illustrator format, something that might be not that easy to achieve, but it is not impossible.
DSF format is still supported in Corel Technical Suite (Corel Designer) so it's possible to recover the drawings using the software and then export it to Adobe Illustrator format. Maybe some other vector software can be used as well, but overall the options will be always limited.