Most data can be exported from the report's screen in Inventory Planner. To export a report:
Go to your desired report and configure:
Which columns appear in the report - any enabled column will be included
The order the columns appear in
The report filters
Click "Export" at the bottom of the page
Reports are exported as CSV files.
Some data, such as individual stock orders, can be exported in other formats. To learn more about exporting stock orders, read this article.