Is there a special cube for charging an iPhone in France?

Apple products are universal, so you won't be needing any voltage converter. As KillerFocus stated, you'll only need to purchase an adapter. Apple sells an official adapter kit for everywhere in the world here - Apple World Travel Adapter Kit ($29.00) - Apple

However, you can also purchase them separately by third-party means. They should look similar to the examples below-

Enjoy your trip!

Assuming that you are in the US, France uses a different plug - type c and e. The good news is that you don't need a coverter - only an adapter. They are readily available at a number of online retailers.

Here is an adapter that has worked well for me:

amazon.com/EPICKA-Universal-Travel-Adapter-Power/dp/B078S3M2NX/ref=sr_1_5?crid=VVYZF7W5TW6K&keywords=travel+adapter&qid=1657070838&sprefix=travel+adapter%2Caps%2C81&sr=8-5