Admins can import content directly from Confluence.
Exporting all of your content from Confluence
First, create a site backup in Confluence. Click Settings in your Confluence sidebar, and then choose Backup manager.
In the Backup manager page, check the box for Backup attachments under Moving to Confluence Server and click Create backup for server.
Once the zip file of your backup is created, it will appear at the bottom of the page — click on it to download it.
Exporting a single space from Confluence
In the space, go to Space settings → Content tools → Export. Choose XML, and click Next.
You can then choose to Full export to export everything in the space, or Custom export to export certain pages from the space.
Once the export is complete, click to download it.
Importing from Confluence into Slab
Open Slab and go to Import & Export in Team Settings. Next to Confluence, click Import. You can then drag and drop your files from Confluence, or click to upload them.