Various font converters like FontForge or similar should be able to help you with conversion of SFD font databases to a WOFF font format. Both formats are not that common, but it should work just fine.
Convert Fontforge Spline Font database file format to Web Open Font Format package file.
We have found 3 software records in our database eligible for .sfd to .woff file format conversion.
Multiplatform software - convert sfd to woff on any platform
A free outline font editor
Convert from sfd file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned sfd to woff. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
On-line services software - convert sfd to woff on web
A free web service for font conversion
A tool for online conversion of fonts