Use the dedicated JSON plugin : construct.net/en/make-games/manuals/construct-3/plugin-reference/json
Do not set Text.text to be equal to AJAX.LastData, but instead use the "Set JSON" action of the JSON object.
Then, you can set Text.text to be equal to JSON.Get(YOUR_PATH).
To define exactly what YOUR_PATH is supposed to be, it depends on the JSON data you are getting with AJAX.
You unfortunately do not provide the exact structure for the data you get, so it is hard currently to help you further with this.
Nevertheless, you can check this example that makes use of JSON data and adapt it to your own project accordingly.