is there any way to adjust an save file to newer version or newer mod?

[caesius]

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

[Coenmcj]

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.