1. In the Contents pane, point to the desired layer. Click the More Options button and select Show Item Details.
2. In the Item Details page, click the drop-down next to the layer name under 'Layers', and select Service URL.
Example:
3. Scroll down to the bottom page and click Query, and the HTML dialog box comes up. In the 'Where:' field, type '1=1' and click the 'Query (GET)' button at the bottom.
Below the HTML dialog box, there is '# results: x'. This shows the number of records. For example, '# results: 5'. This shows that there are 5 records for the feature service.
Example: