How can I replace contains from C++20 in C++11 code? [closed]

I feel, like it's something easy, but I can't find an answer by myself.

auto iterator = _map.find(key);
DeliveryData smth;
if(/*check*/)
    smth = iterator->second;
return(smth);

How can I check for the result of find-method in this context? I know about contains in C++20. Any other method?

I forgot to say that find doesn't returns C++ expression of type bool or a type that can be converted to bool. It was not clear to me what should I use to compare with iterator.