Get unity to stop showing an error

Okay i am going to make an app with guns. I am okay with blender but i’m not great with it, and my models especially guns don’t look as good. So i went online and downloaded some. I can import it into unity perfectly fine with no issues. But Unity keeps saying "3ds Max could not be found.
Make sure that 3ds Max is installed and the max file has 3ds Max as its ‘Open with’ application!
"
thing is im 13 and i can’t afford 3ds max, and the models work perfectly fine so why would I? How do i get rid of the annoying errors so i can just use them. They work and look and import just fine.

the models you are downloading have the same model in multiple formats. You are importing all of them, including the ones with the file extension .3ds , delete the .3ds files from your project.