How can I move tasks from "all work" to the backlog in Jira?

[Monserrat Dominguez Martinez]

I have completed a sprint and selected passed the unfinished tasks to a New Sprint. Now, I can't find my "new sprint" and the unfinished items are not in the backlog. However, I can see them in "All work". 

How can I get those tasks back in the backlog so I can recreate the new sprint with them?

Thanks! 

[Mohanraj Thangamuthu]

Hello, Good day. Please check the JQL query used on the board and make sure this Task is included in the query. If its included then go to board settings >> column mapping and make sure the status of the missing Task is mapped. Thanks