Try to Google this kind of stuff first. :)

import json

array = [1, 2, 3]
jsonArray = json.dumps(array)

By the way, the result you asked for can not be achieved with the list you provided.

You need to use python dictionaries to get json objects. The conversion is like below

Python -> JSON
list -> array
dictionary -> object

And here is the link to the docs https://docs.python.org/3/library/json.html

To solve this, you need to split the input list into chunks, by 7 in your case. For this, let's use this approach. Then, use a list comprehension producing a list of dictionaries:

>>> from pprint import pprint
>>> l = [['String 1'],['String 2'],['String 3'],['String 4'],['String 5'],
... ['String 6'],['String 7'],['String 8'],['String 9'],['String 10'],
... ['String 11']]
>>> def chunks(l, n):
...     """Yield successive n-sized chunks from l."""
...     for i in range(0, len(l), n):
...         yield l[i:i+n]
... 
>>>
>>> result = [{"title%d" % (i+1): chunk[i][0] for i in range(len(chunk))} 
              for chunk in chunks(l, 7)]
>>> pprint(result)
[{'title1': 'String 1',
  'title2': 'String 2',
  'title3': 'String 3',
  'title4': 'String 4',
  'title5': 'String 5',
  'title6': 'String 6',
  'title7': 'String 7'},
 {'title1': 'String 8',
  'title2': 'String 9',
  'title3': 'String 10',
  'title4': 'String 11'}]

When there are internal properties mark them as a JsonProperty, otherwise go with SimpleSamples recommendation.

using System.Collections.Generic;
using System.Diagnostics;
using Newtonsoft.Json;

namespace ObjectToJson
{
    class Program
    {
        static void Main(string[] args)
        {
            var i1 = new Item
            {
                Name = "test1",
                Value = "result1"
            };

            var i2 = new Item
            {
                Name = "test2",
                Value = "result2"
            };

            ReturnData returnData = new ReturnData();

            var items = new List {i1, i2};


            returnData.Type = "type1";
            returnData.Items = items;

            var json = JsonConvert.SerializeObject(returnData, Formatting.Indented);

            Debug.WriteLine(json);

        }
    }
    class ReturnData
    {
        [JsonProperty]
        internal string Type { get; set; }
        [JsonProperty]
        internal List Items { get; set; }
    }

    public class Item
    {
        public string Name { get; set; }
        public string Value { get; set; }
    }
}

Output

{
  "Type": "type1",
  "Items": [
    {
      "Name": "test1",
      "Value": "result1"
    },
    {
      "Name": "test2",
      "Value": "result2"
    }
  ]
}