Every result (item/record) from a search module will output a bundle. To “combine” them into a single structure, you’ll need to use an aggregator of some sort.
Aggregators are modules that accumulate multiple bundles into one single bundle. An example of a commonly-used aggregator module is the Array aggregator module.
You can aggregate to text too, then add the wrapping JSON object around it.
Links
Here are some useful links and guides you can use to learn more on how to use the Make platform, apps, and app modules. I found these useful when I was learning Make, and hope they might benefit you too —