I have tried the iCloud/finder but it says that all devices are offline.
Both devices would have had to have been previously set up for Find My.
But, even if they were, the devices must have good battery power and an active Internet connection to show up on the Find My map. If they don't, they will show up as "offline".
Another way to say the same thing......if the battery runs down on a device or the device does not have an Internet connection at its current location, then it will show up as "offline" and will not be visible on a map.
When you see "offline", all that you can do is keep trying.