To export this you will need to create a template:

1. Include SKU as the first column
2. Under attributes, search for "quantity". You should see  an option for each of your warehouses followed by the word "quantity" in the dropdown menu.
3. Select the warehouse for which you want to export inventory. Be sure to click the "plus button" when adding another warehouse.
4. Click "Create Template" 
5. Under custom templates, click on the Inventory Template you just created and run the export

   

To update your inventory:

1. Once the template is exported (downloaded), open the excel file
2. Add in the correct inventory to each warehouse
3. Upload the CSV file by using the same template you created.