The prefix 039928 is the area code for Möllenhagen. And Möllenhagen is located in Germany. If you are outside United States of America and you want to call a person in Möllenhagen, in addition to the area code, you need the country code for the country you wish to call. The country code for United States of America is +49, so if you are in United States of America and you want to call a person in Möllenhagen, you have to prefix that person’s phone number with +4939928.
As an alternative to +4939928, which you have to place in front of the telephone number of a person in Möllenhagen in order to call them from United States of America, you can also use 0114939928.