Final answer:
The information provided does not specify the number of expeditions Michel Brunet made before his discovery; therefore, a precise answer cannot be given based on the available data.
Step-by-step explanation:
The question pertains to the number of expeditions undertaken by Michel Brunet before making his significant discovery. However, the information provided does not clearly state the number of expeditions Michel Brunet participated in before finding his object of search. It can be inferred that there were several undertakings by various individuals, such as the expeditions led by Lieutenant Brenans and Jean-Marie Chauvet, who found prehistoric caves and rock art, but specific details about Michel Brunet's expeditions are not mentioned in the provided passages.