You can utilize below FlexReport query to retrieve the Vcore numbers along with resource group details
{
"sqlStatement": "SELECT timeInterval_Month AS Month, SUM(ActualCostInBillingCurrency) AS SUM_ActualCostInBillingCurrency, SUM(ActualCostInReportingCurrency) AS SUM_ActualCostInReportingCurrency, ResourceGroup AS ResourceGroup, AdditionalInfo AS AdditionalInfo FROM AZURE_COST_USAGE WHERE (AdditionalInfo LIKE '%vCores%') GROUP BY timeInterval_Month, ResourceGroup, AdditionalInfo",
"needBackLinkingForTags": true,
"dataGranularity": "MONTHLY",
"timeRange": {
"last": 12
},
"limit": -1
}