Hello,
I found the way to import saves (ingame saves - battery saves) from DSTWO to DraStic emulator using Desmume:
1/ Copy filename.sav from your DSTWO's rom folder.
2/ Start DEsmume and load rom (bur sure that the rom name is renamed like the filename.sav from point 1.)
3/ Import filename.sav (let AUTO selected when prompt) with DEsmume menu (file / import backup memory)
4/ Export backup memory and name the file like the rom present in DraStic's rom folder eg: filename.dst
5/ Put filename.dst in .../DraStic/backup/
6/ Don't forget to make a savestate while playing with DraStic.
Cheers.