Get it from Office Store link https://store.office.com/app.aspx?assetid=WA104380263
Click on the above link and, you will see the webpage of Excel-to-JSON on Office Store.
Click on the “add” button.
The next page you will see will show that you can open the add-in in Excel/Excel Online.
Now go to Excel 2013/2016 or Excel Online.
Insert Tab > My Add-ins.
In the Add-ins for Office box, find “Excel-to-JSON”.
Double-click the add-in to start it.
Note that you should select at least two rows as the first row will be considered as header.
Prepare your Excel sheet
Select data you’d like to convert
Click on “Go” button
You will later see the converted JSON below the “Go” button
Later you can “copy+paste” / “copy to clipboard” JSON and save it to your computer