You cannot directly see a chat that was deleted from WhatsApp unless you have a backup or the messages were saved elsewhere
Restore WhatsApp from a recent Google Drive backup on Android
Restore WhatsApp from a recent iCloud backup on iPhone
Check if the chat is still visible in archived chats
Ask the other person to resend the messages or export the chat
Check notification history on Android if message previews were enabled
Check any linked devices where the chat may still be open
Look for exported chat files saved on your phone or cloud storage
Check local backups on Android if available
Use third-party recovery tools only with caution and only from trusted sources