The question is complicated by the fact that there is no such thing as a single mind called the average French citizen. Each French citizen living in France in 1942 had different experiences, pending on their location, and access to certain knowledge. Its impossible to say what an average person knew or didn't know and if they knew how much they knew. To complicate matters more the answer is going to be somewhat subjective, how does one quantify the average French citizen? And how does one quantify the average body of knowledge of the average French citizen?

These answers from the FAQ might help you understand a little bit more about the public/available knowledge of the death camps:

https://www.reddit.com/r/AskHistorians/comments/6696bw/new_understanding_of_allies_knowledge_of_the/dggmqh6/ --- courtesy of u/becauseiliketoupvote

https://www.reddit.com/r/AskHistorians/comments/121iw5/how_did_it_become_common_knowledge_that_nazi/c6rh8qn/ --- courtesy of u/estherke