A try to convert from char* to wchar_t* but doesn't work with non-English languages

Question

I want to convert a string from char* to wchar_t* but that string is any language other than English for example (Russian, Chinese, Arabic, etc). I have tried to do that by the following:

// This is just an example of conversion
const wchar_t * ToWide(const char* mbStr) {
    const size_t cSize = mbstowcs(NULL, mbStr, 0) + 1;
    wchar_t* wc = new wchar_t[cSize];
    mbstowcs(wc, mbStr, cSize);
    return wc;
}

int main() {
    // just the first one is the only that works fine
    wcout << ToWide("Hello");  // (English) The result: Hello
    wcout << ToWide("Привет"); // (Russian) The result: ???????
    wcout << ToWide("你好");    // (Chinese) The result: ??
    wcout << ToWide("مرحبا");   // (Arabic) The result: ع╤═╚╟
}

Why did this happen and how can it be solved or what is the right way to convert from char* to wchar_t*?