Hi,
Welcome to the community!
Your version is past EOL. You should upgrade to either the latest version or the current LTS at your earliest convenience. Your upgrade path is:
8.5 → 8.9.9 → 9.6 (last step optional)
You may find the Upgrade Guide and the LTS-to-LTS Upgrade Notes helpful. If you have questions about upgrading, feel free to open a new thread for that here.
Once you’ve upgraded, try retrieving the data via the UI. The best way to master the API is to perform the desired action via the UI and eavesdrop to see which calls the UI made to accomplish the action.
You may also find this guide helpful.
Ann