When you say “my character is not in the folder,” do you mean that there is no unreal asset/blueprint in the path Blueprints/Character/TopDownCharacter in the Content directory?
If so, yes, you will get an error.
If that class does exist, try specifying it without the .TopDowCharacter_C part of the string.
Assuming the blueprint class exists, then if you right-click the blueprint class in your content browser, and select “Copy Reference,” and then switch to your code editor and paste the string, what comes out?
E g, if I “Copy Reference” on a test asset, and paste into the text editor, it will print "Blueprint'/Game/Test/BP_Generator.BP_Generator'"
(Note the lack of _C in the name!)
The string that the ClassFinder actually wants, though, is "/Game/Test/BP_Generator"
The other thing to watch out for – in your code, you’re asking for a subclass of UClass. That’s not what the argument to ClassFinder wants – it wants the actual class that your class implements. So, something like UObject, or UActor, or so on. In your case, you probably want ACharacter as the superclass of the class.