In the "Log" tab of the "Git" tool window, select and right click the revision prior to commits to re-order. Choose "Copy revision number":
Use the "Git -> Rebase" menu.
Paste the revision into the text field.
Remove any other options enabled and add
Use up/down button to re-order the commits where the commits are ordered top-to-bottom, oldest-to-newest:
Click "Start rebasing". You will be prompted to resolve any conflicts that might occur due to the re-ordering.