Hello Matija,

If you have the language file from Version 9 you can export it from step 1 - general settings - Loanguage Content Management and then import it in the same position in Version 10. If you don't have the file from Version 9 you can create the translation in Version 10 in the Language content management which can be opened with the button after "Content Language".

If you require any further information, please feel free to write back.