Assuming that you have updated your iPad9 to iPadOS 15.1, first open the Safari sidebar - and open the Reading List.
With the Reading List visible, you can either individually delete saved articles (swipe to the left, then tap Delete) - or delete multiple items…
To delete multiple items from the Reading List, tap the Edit button at bottom-right of the sidebar. You can now select multiple items by tapping each item that you wish to select for deletion - or swipe your finger down the left-edge to rapidly select the list. When you have finished your selection, tap the Delete button at bottom-left of the sidebar.