Can I Get Number of Unread Count in a Channel ?

No, you can’t. The number of unread counts only exist for 1-on-1 and Group type. For further information regarding difference among 1-on-1, Group, and Channel you can refer to the docs below: 

Android: https://documentation.qiscus.com/chat-sdk-android/chat-room-types#chat-room-type-comparison-table

Javascript: https://documentation.qiscus.com/chat-sdk-javascript/chat-room-types#chat-room-type-comparison-table

iOS: https://documentation.qiscus.com/chat-sdk-ios/chat-room-types#chat-room-type-comparison-table