Is there a way to search through a text message conversation that is years long?

Greetings dddunne,

You can search for messages on your iPhone by following these steps:

"Reveal the search field in Messages

1. In Messages, open your list of conversations.
2. Swipe down to reveal the search field.
3. Enter what you want to find and tap search." Search within your text messages on iPhone

We hope this helps!

Sincerely.

Hi there dddunne,

Searching within a specific thread or conversation in Messages isn't a supported feature. You can provide feedback using this link if you'd like: Feedback - Messages - Apple

Take care.