You can archive messages on Facebook to move messages into a different folder, away from the main list of conversations. This organizes your conversations without deleting them, which is useful if you don’t need to message someone but still want to keep the texts.
How to find your archived messages in Facebook Messages!
If you can't find archived Facebook messages, use the instructions below. Facebook messages can be accessed through Facebook and Facebook Messenger.
To manually access your archived messages, follow these steps (if you're using Messenger.com, skip to step 3):
For Facebook.com, open Messages. It’s at the top of Facebook on the same menu bar as your profile name.