You just have to be creative with your google searches! I realized this semester you can argue pretty much anything by citing some semi-relevant sources.
So you're trying to argue how millenials aren't growing up. This is your thesis. If you search "millenials not growing up" you will probably get 0 hits. But you can search some other stuff - your evidence. Then you just need to tie the evidence to your main thesis or argument.
For example. How can we show millenials are not growing up? It depends on how you define or measure growing up. Off the top of my head, we should be able to find articles that show
-millenials have more debt now than the previous generation did (adjusted for inflation)
-millenials earn a smaller wage than the previous generation (adjusted for inflation)
-millenials are marrying less / later
-millenials are less certain of what they want to do in life
-millenials stay at home with their parents till a later age
Then your job is just to connect these pieces of information to the thesis you are trying to prove. Ez-peezy A (Eh?)
Good luck