Gitpage or Gitbook documentation (transitioning from Confluence)

My project is looking at transitioning from Atlassian products to Gitlab - I’m concerned about transitioning our vast documentation that is currently in Confluence to Gitlab’s wiki. Someone mentioned Gitlab has Gitpage and Gitbook available that could be used but I cannot find any information. Can anyone direct me?

Otherwise, any suggestions on going from Confluence to Gitlab Wiki? Or, should we look elsewhere for our documentation needs?