how do I get messages in the cloud

The messages in iCloud are the same messages that are on your device. All that using messages with iCloud does is to keep them in sync across all devices. You can’t store messages in iCloud or delete e message on your device and have it still reside in iCloud.

So if you want to see the messages in iCloud, look in the messages app on your device. They are identical to what is being synced with iCloud.