my old version savefile got crashed when i load it in newer modpack.
um...is there any way to convert or adjust it? by program or by hand eitherway
Depends on the mods used really, you could technically go into the save file and obliterate any mentions of obsolete items or objects, however that's putting you open to a game breaking bug here and there.
Judging by how you said Modpack though, then you would be much better off starting anew.