How to find the name of a field if its not provided in html?

Question

I'm learning Postman and I have an exercise to do. I should create wagers with a sports betting app using Postman. The following POST http://localhost:8080/sportsbetting-web/addWager? should be used to create a new wager, by passing parameters. However one of the parameters should be chosen from a drop-down list. The html of that is:

<select ng-model="wager.outcome" ng-required="true" class="ng-touched ng-not-empty ng-dirty ng-valid-parse ng-valid ng-valid-required" required="required">
  <!-- ngRepeat: outcome in outcomes --><option ng-repeat="outcome in outcomes" ng-value="outcome" class="ng-binding ng-scope" value="object:43">Fradi wins</option><!-- end ngRepeat: outcome in outcomes --><option ng-repeat="outcome in outcomes" ng-value="outcome" class="ng-binding ng-scope" value="object:44">Draw</option><!-- end ngRepeat: outcome in outcomes --><option ng-repeat="outcome in outcomes" ng-value="outcome" class="ng-binding ng-scope" value="object:45">UTE wins</option><!-- end ngRepeat: outcome in outcomes -->
</select>

which contains options, like:

<option ng-repeat="outcome in outcomes" ng-value="outcome" class="ng-binding ng-scope" value="object:43">Fradi wins</option>

I tried using OPTION, outcomes in outcome, outcome, wager.outcome as the KEY to pass values with it. I tried passing values as the html described them (value="object:43"), however I always got 400 bad request.

E.g.: Key: outcome Value: option:45.

So my question is, how can I find the attributes name, or whatever I have to pass the params into?