How do I know the number of licenses available

For 'device' licenses, the only way I've seen to see the number installed, or available, is to open CCP and start the process to create a new installer.  When you select the company name it'll tell you how many have been installed.

For other licenses I think you can sign into your Adobe admin account and it'll show you.

https://creative.adobe.com/team/admin

If you are talking about device licenses, you can't.  There is no place anywhere in the CC portal or in the apps themselves where the number of licenses is displayed.  In fact if you only have device licenses, the portal will actually clearly tell you that you have '0 licences' when you might have over 100 device licenses, as the portal only seems to be able to deal with user licenses.