MQTT.input - JSON - save/convert Int as String

Hi, I am looking for a way to store the output of a json as a string in influxdb. the json is quite simple:
{“serial”: “AA123”, “time”: “2020-03-06T13:00:00+00:00”, “store”: 0} or
{“serial”: “AA123”, “time”: “2020-03-06T13:00:00+00:00”, “store”: 1} or
{“serial”: “AA123”, “time”: “2020-03-06T13:00:00+00:00”, “store”: 2}

I use “serial” as tag key, “time” as timestamp and i want to have “store” as String: e.g.: if store=0 --> save string “Green”; if store=1 --> save string “Blue”, etc.

I tried to work with process.enum-plugin, but it did not do transform, the field type is/stays float, altought i set json_string_fields = [“store”].

Is there another possibility? maybe with GJSON? How/Where to configure that?
Thank you in advance…