French – as a distinct ethnolinguistic group tied to the French language and identity – emerged after the fall of the Western Roman Empire, around the 5th–9th centuries CE, when Latin-speaking Gallo-Romans blended with Franks and other Germanic peoples.
The ancestors (Gauls, Romans, Franks) lived in what is now France for millennia, but “French” in the modern sense is about 1,200–1,500 years old.
Iranians – in the sense of peoples speaking Iranian languages (Persians, Medes, Parthians, etc.) – have existed since at least the 1st millennium BCE. The Persian identity (linked to the Achaemenid Empire) is about 2,500+ years old, but Indo-Iranian roots go back 3,500+ years.