I just searched for “c++ float to string unreal” and it pointed me here: https://answers.unrealengine.com/questions/3716/convert-float-to-fstring-c.html
In your code: FString ObjectPos = FString::SanitizeFloat(Pos.X);
So you have to go from the FString class which has a converter for floats. I expect some things are like this: if the converter you are looking for isn’t on what you are converting FROM check and see if there is a converter on what you are converting TO. And in a pinch there is always google, stackoverflow, or answers.unrealengine.com