Add a Metadata Filter to a vco Query

Add a Metadata Filter to a  VCO Query - how to use vco vcfilter ?? If there is a way I need the syntax to be able to use the below call.

I have to make a search based on key and value.

vcd rest call:

https://x.x.x.x/api/query?type=organization&format=records&fields=metadata@SYSTEM:first&filter=metadata@SYSTEM:first==STRING:world

vco:

what will be the expression for metadata??

var expressionOrgVal1 = new VclExpression(VclQueryOrgField.DISPLAYNAME, "Mr*", VclExpressionType.EQUALS);

////??/////var expressionOrgVal2 = new VclExpression(VclQueryOrgField.value, "metadata@SYSTEM:first==STRING:world", VclExpressionType.EQUALS);

var expression = new Array(expressionOrgVal1, expressionOrgVal2);

var filter = new VclFilter(expression,VclFilterType.AND);

//var filter = new VclFilter(expressionOrgVal1);

var params = new VclQueryParams();

var orgRef = new VclReference();

params.setFilter(filter);

params.addMetadataField("first", VclMetadataDomain.SYSTEM);