get parameter from action calling

Hi there! I'm new in mendix, so don't judge too hard.

what I need:
- from client side call microflow that will will return list of objects with selection parameters
what I do:
- created microflow with parameter - parameterName
- calling action from client in such way

mx.data.action({
    params: {
        applyto: "set",
        actionname: "MyFirstModule.MicroflowName",
        xpath: "//MyFirstModule.EnetityName",
        constraints: '[parameterName="parameterValue"]',
        sort: [["parameterName", "asc"]],
    },
    origin: this.mxform,
    callback: function(obj) {
        console.log('got list', obj);
    },
    error: function(error) {
        console.log('got error', error);
    }
});

- in microflow created parameter with parameterName and type string and passing it to Action with type Retrieve Objects

['parameterName' = $parameterName]

- also tried before Retrieve Objects Create Variable, where will store parameterName

My problem:
- parameter that I'm trying to retrieve is empty

My question:
- where I'm wrong