Error when program loads

I have installed minifrontpage and when I put {module 239} on the page for it to load - I get this error:

[4.0] Error: Call to undefined method Joomla\CMS\Application\AdministratorApplication::isAdmin()

I am running joomla 3.9
    Replied by admin on Monday, July 05 2021, 11:07 PM · Hide· #1
    Hi, it looks like you have installed incorrect minifrontpage version. There are two minifrontpage installation files when you unzip the file. One for Joomla 3 and the other one for joomla 4. Please make sure you install the minifrontpage for Joomla 3 (
    Please post rating at the Joomla! Extensions Directory -
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