Galaxy S memos (.smm) do not contain contacts data, so smm to vcf conversion seems to be impossible. You would need a full backup of your device in order to extract and save contacts from it.
Convert Samsung Galaxy S memo exported data to vCard contacts.
We have found 2 software records in our database eligible for .smm to .vcf file format conversion.
Microsoft Windows software - convert smm to vcf on Windows
A free software for managing of latest Samsung mobile devices
Convert from smm 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 smm to vcf. 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.
Apple macOS / Mac OS X software - convert smm to vcf on OS X
Management and sync utility for Samsung mobile devices