How do you go to the first message in iMessage on Mac?

*Running Mac OS Catalina 10.15.1 *

I'm trying to print off one text message thread on Mac to save as PDF and then print later.

The messages from this thread span over 2 and a half years (long distance relationship). Yes, it's like 50 gb from one person!

Instead of manually scrolling to the very top which will destroy my computers fan and take me 1 week, is there a way to just show the entire thread? Or just somehow reach the top.

*I can see all our images sent under the "Details" option next to her name (1000's of images, so I know the entire thread is there*

*Manually saving the Messages files in the backend will not work as this seperates all Messages on Mac by month*

*You have to have all messages loaded and displayed before clicking Print or saving as a PDF (otherwise it just loads the most recent texts, like 30 pages).*

THANK YOU SO MUCH!