Old Joomla links goes to homepage of new WordPress?

Have recently switched over from Joomla to WordPress.

Old Joomla site, all of our links were in the following structure:
“www.****.com/?option=com_content&view=article&id=20&Itemid=146”

Our new WordPress site we have it working in the better structure as follows:
“www.****.com/page1”
“www.****.com/page2”
etc.

The problem is, Google is still has indexed the old Joomla links and instead of a 404 error, it now shows our homepage with the old Joomla address in the URL bar of the browser.

Is this a common thing? I don’t know how to fix this. Please help. Thanks.

Note, if you try to go to a WordPress page that doesn’t exist, it will properly show a 404 error page.
ie. “www.****.com/pagenotexist/” —–> 404 error page.