First, let's write our code for reading and writing and then see how we will use it.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using System; // Our library necessary for file operations.

public class UBJsonDataManager : MonoBehaviour
{
    public static dynamic ReadJSONData(string dataPath, Type dataType) // We create a function for reading JSON, we require the file path and type.
    {
        string jsonData = System.IO.File.ReadAllText(dataPath); // We read our file
        dynamic returnedData = JsonUtility.FromJson(jsonData, dataType); // We convert the file we read from JSON to the desired type.
        return returnedData; // We return our file.
    }


    public static void SaveJSONData(dynamic data, string dataPath) // We create our function to create a JSON file, requiring our data and file path.
    {
        string jsonData = JsonUtility.ToJson(data); // We convert our data to JSON.
        System.IO.File.WriteAllText(dataPath, jsonData); // We save our data.
    }
}

Now let's see how to use this script we created.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class UBJsonDataManagerExample : MonoBehaviour
{
    UBJsonDataManagerExampleSingleData singleData; // We call the class for single data. We enter the values we want through the editor.
    UBJsonDataManagerExampleWrapper multipleData; // We call the class for an array. We enter the values we want through the editor.

    UBJsonDataManagerExampleSingleData readedSingleData; // We will print the data we fetch here.
    UBJsonDataManagerExampleWrapper readedMultipleData; // We will print the array data we fetch here.

    public void SaveData() // We created a function to save the data.
    {
        string singleDataPath = Application.dataPath + "/singleData.json"; // We entered the location of our single file.
        string multipleDataPath = Application.dataPath + "/multipleData.json"; // We entered the location of the array file.

        UBJsonDataManager.SaveJSONData(singleData, singleDataPath); // We saved our single data, entered the data and file path to save.
        UBJsonDataManager.SaveJSONData(multipleData, multipleDataPath); // We saved our multiple data, entered the data and file path to save.
    }

    public void ReadData() // We create a function to read the data.
    {
        string singleDataPath = Application.dataPath + "/singleData.json"; // We entered the location of our single file.
        string multipleDataPath = Application.dataPath + "/multipleData.json"; // We entered the location of the array file.

        readedSingleData = UBJsonDataManager.ReadJSONData(singleDataPath, typeof(UBJsonDataManagerExampleSingleData)); // We fetched our single data, sent file path and data type.
        readedMultipleData = UBJsonDataManager.ReadJSONData(multipleDataPath, typeof(UBJsonDataManagerExampleWrapper)); // We fetched our multiple data, sent file path and data type.
    }

    private void Awake()
    {
        SaveData(); // We saved the data.
        ReadData(); // We fetched the data.
    }

}


[System.Serializable]
public class UBJsonDataManagerExampleWrapper // We need to create a wrapper to save array data. We are creating a wrapper.
{
    public UBJsonDataManagerExampleSingleData[] uBJsonDataManagerExampleSingleDatas; // To save multiple data, we created an array inside the new class.
}

[System.Serializable]
public class UBJsonDataManagerExampleSingleData // We are creating a class to create data, thanks to this we can edit data in the editor or fetch from a JSON file.
{
    public int exampleSingleDataInt;
    public string exampleSingleDataString;
}

Yes friends, if you have any questions about creating and reading JSON in Unity, you can ask me in the comment section below. Have a nice day.