Hi @Claire_Tompkins, thanks for reaching out!
The conversations tab is now called “Messages” and it’s still located in your project header. These updates have been announced in our announcements category as soon as they rolled out. You can see more details about these launches here: Introducing Project Overview, Project Brief, and Messages.
If you aren’t yet, I’d recommend you to Follow our Announcements category to keep up to date with what’s new in Asana! 
- #5