У вас в contents не объект, а ещё одна JSON-строка.
{
contents: "{\n \"destination_addresses\" : [ \"Kyiv, Ukraine, 02000\" ],\n \"origin_addresses\" : [ \"Luhansk, Luhansk Oblast, Ukraine, 91000\" ],\n \"rows\" : [\n {\n \"elements\" : [\n {\n \"distance\" : {\n \"text\" : \"821 km\",\n \"value\" : 821154\n },\n \"duration\" : {\n \"text\" : \"11 hours 32 mins\",\n \"value\" : 41522\n },\n \"status\" : \"OK\"\n }\n ]\n }\n ],\n \"status\" : \"OK\"\n}\n"
status: {
content_length: 530
сontent_type: "application/json; charset=UTF-8"
http_code: 200
response_time: 330
url: "https://maps.googleapis.com/maps/api/distancematrix/json?origins=Луганск&destinations=Киев&key=AIzaSyCO9I-9cmBpuwUJEdBcNe5F3AGN4iW_Dzs"
}
}
Её надо снова распарсить
const data = JSON.parse(content.contents); 
