UE5.1 Documentation mentions:
Outer object to look inside. If this is ANY_PACKAGE it will search all in memory packages, if this is null then InName should start with a package name.
So I replaced ANY PACKAGE with nullptr.
Then I found the class I was looking for in UE Content Drawer and copied reference.
UClass* classObj = FindObject<UClass>(nullptr ,L"/Script/CoreUObject.Class'/Script/[MyProjectName].[MyClassName]'");
I hope that will be helpful.