Goldendict is not a file format. The program goldendict supports many file formats (StarDict/Babylon/Lingvo/Dictd/Aard...). You should be fine if your dicts are already in stardict format. If not you can convert them.
The same tool used to convert from different source formats to stardict can be used to convert them to kobo format. See the tool and the list of supported formats in
https://github.com/ilius/pyglossary#supported-formats