From the Import/Export page, click on Item details under the Exports column.
On the window that appears, click the Export button at the bottom.
After a few moments, the Items button will appear allowing you to download the newly exported item details CSV file.
Make copies of this file and keep them somewhere safe in case you ever need to restore your data at any point in the future.
TIP: You can also Automate stock exports for historical record of inventory snapshots