Sorry, this is not possible.
As of now, the responses are paginated and you’ll get 30 conversations in each page. One possible solution I could think of is getting the total conversations available as part of payload. So that you can hit with the right end threshold to get the latest tickets & sort as above. Sorting would not cause any API rate limit error, making repeated calls through the pagination might lead to.
I’ll request the team to get this be added to tracker of feature requests (if not already) as I can find other instances of tickets requesting the same - How to fetch latest 10 conversations in a ticket - #12 by RobAtOpinyin
Thanks