Open the Messages app
Tap the search bar at the top
Enter a contact name, phone number, keyword, or phrase
Scroll through the search results to find older messages
Open the conversation and swipe down to load earlier messages
Use the search bar within the conversation if available
Check archived or hidden conversations if you use a third-party messaging app
Restore from an iCloud or computer backup if the messages were deleted
Go to Settings
Tap your Apple ID
Tap iCloud
Check whether Messages in iCloud is turned on
If needed, sign in with the correct Apple ID on the iPhone
Search for attachments by opening the conversation and tapping the contact name
Use Spotlight Search by swiping down on the Home Screen and typing a keyword from the message