Extension of international internship in France
You need to talk to your advisor and, perhaps the supervisor, also any department that deals with internships.

Believing a blog, written by someone who is not in actual charge of the internships for your institution, is not likely to have the correct information.

Also, if you have had 3 years of a course then that may well mean 3 * 6 months of internships may be possible... But that is detail to discuss with those who know for your position.