The safety of your drawings depends on where you store them.

Drawings Stored in iCloud Drive

Yes, your drawings are safe. If you store your work in the iCloud Drive folder within Concepts, the files will remain in your iCloud account even if you lose your device or delete the app.

Drawings Stored Locally (On This iPad)

These drawings are not automatically safe. Work saved under On This iPad in the Gallery exists only on that specific device. If the device is lost or the app is deleted, these drawings will be permanently lost unless you have a recent iCloud backup of your entire device from which you can restore.