To find the statusID, you can run REST API Pull Request Statuses – List firstly. It will list all the statuses associated with a pull request.

GET https://dev.azure.com/{organization}/{project}/_apis/git/repositories/{repositoryId}/pullRequests/{pullRequestId}/statuses?api-version=7.1-preview.1

Sample response:

{
  "value": [
    {
      "iterationId": 1,
      "id": 1,
      "description": "Coverage status check queued for TestPRTrigger",
      "context": {
        "name": "codecoverage",
        "genre": "testprtrigger"
      },
      "creationDate": "2024-09-10T06:32:27.426169Z",
      "updatedDate": "2024-09-10T06:32:27.426169Z",
      "createdBy": {
        "displayName": "Azure Pipelines Test Service",
        "url": "***",
        "_links": {
          "avatar": {
            "href": "***"
          }
        },
        "id": "***",
        "uniqueName": "",
        "imageUrl": "***",
        "descriptor": "***"
      }
    },
    {
      "iterationId": 1,
      "id": 2,
      "state": "pending",
      "description": "Coverage status check in progress for TestPRTrigger",
      "context": {
        "name": "codecoverage",
        "genre": "testprtrigger"
      },
      "creationDate": "2024-09-10T06:33:38.1173998Z",
      "updatedDate": "2024-09-10T06:33:38.1173998Z",
      "createdBy": {
        "displayName": "Azure Pipelines Test Service",
        "url": "***",
        "_links": {
          "avatar": {
            "href": "***"
          }
        },
        "id": "***",
        "uniqueName": "",
        "imageUrl": "***",
        "descriptor": "***"
      }
    },
...

Update

Pull request status provides a way for services to associate simple success/failure type information with a pull request. You need to configure some branch policies on your target branch, then you can get the PR status.

See more info about PR status from Customize and extend pull request workflows with pull request status.