How do I disable the Auto Delete Old Conversations?

Go to Settings > Messages and scroll down to "Keep Messages" and change that to "Forever."

If the messages weren't deleted, you should be able to view them in the Messages app.

If they were deleted within the last 30 to 40 days, see the following: Recover deleted text messages on your iPhone or iPad - Apple Support

My setting is at Forever but I can only see my text messages starting in January 2024. I do I get older messages