Cannot update or use iMovie after updating macOS
I own a 27 inch iMac (late 2013) and yesterday I upgraded my operating system for the first time, from Yosemite, to Mohave, to Catalina (as new as my computer can allow), and now iMovie will not work, so when I go to the app store to update iMovie, it says I need macOS 11.5.1 or later, but the problem is that the version I have is 10.15.7, and thats as new as I can go. (See Screen Cap). Now I cannot use iMovie, and I cannot download the new version, and I really could use some help. I make and edit videos for my business constantly and need access to this software badly. Please help.