It depends on your cloud storage provider.
If you are using Strongbox Sync, your database files will not be visible anywhere, there is no "Cloud Drive" app to view them. They do not appear in your iCloud Drive. You need to export them directly from Strongbox if you want to make a copy. See our helpful article here: Strongbox Sync - Frequently Asked Questions.
If you are using iCloud, then you will be able to save or open your databases from the Strongbox iCloud folder in the usual fashion. You should click File > Open or File > Save as appropriate and select the location as usual from the dialog.
For other providers you should use their specific Drive synchronisation software. Google Drive uses ‘Backup and Sync’, Dropbox and OneDrive have their own Mac syncing application. You will find these applications on their respective websites.
Once you have installed that synchronisation software, you will find the Dropbox, OneDrive or Google Drive folder in Finder, where you can load or save your databases.