What do you do?
You need to choose 2 ads and they should be selling the same type of thing. One ad should be prior to 1980 and one should be after 1980. They don’t have to be exact but should be the same type of merchandise. For example, if you choose cigarettes, the ads do not have to be the same type of cigarette.
Then you need to figure out what you are going to say about the ads. What type of “lens” are you using to examine the ads. Are you looking at Sexuality? Race? Gender norms? Traditional housekeeping roles? Stereotypes?