for Umbraco Cloud, get these values from Umbraco Cloud Project Manager -> Settings -> Connection Details -> Blob Storage Connection Details

"Umbraco": {
    "Storage": {
      "AzureBlob": {
        "Media": {
          "ConnectionString": "BlobEndpoint=https://ucmediastoragewelive.blob.core.windows.net/;SharedAccessSignature=[4. Shared Access Signature, without the first question mark]",
          "ContainerName": "[3. Container Name GUID only, no curly braces]"
        }
      }
    },