Delete all messages on iCloud

Hi tiffiny112,

Thank you for reaching out in Apple Support Communities. If Messages is turned on for iCloud in Settings > your name at the top > iCloud > Show All > Messages, then you can go in the Messages app and delete all of the conversation threads. To delete all of the conversation threads, you can open the Messages app > tap on "Edit" in the upper left corner > Select Messages > select all of the threads and tap on "Delete" in the bottom right corner. Keep in mind this will delete the messages across your Apple devices in which you're using the same Apple ID and have Messages turned on for iCloud if needed, here's an article with steps on how to delete the messages: Delete messages on iPhone - Apple Support

Kind regards.