public class CustomSelectOption {
   
    @AuraEnabled
    public String label { get; set; }

    @AuraEnabled
    public String value { get; set; }

}

@AuraEnabled
public static Map<String, Object> getCountryAndProvinceOptions() {
    Map<String, Object> returnMap = new Map<String, Object>();
    List<Custom_Shipping__mdt> customShippingMetadata = [select Country__c,State__c,Countrycode__c,Sattecode__c from Custom_Shipping__mdt];

    Map<String, List<CustomSelectOption>> countryProvinceMap = new Map<String, List<CustomSelectOption>>();
    List<CustomSelectOption> countryOptions = new List<CustomSelectOption>();
    for(Custom_Shipping_mdt customShippingRecord : customShippingMetadata) {
        if(!countryProvinceMap.containsKey()) {
            countryProvinceMap.put(customShippingRecord.Countrycode__c, new List<CustomSelectOption>());

            CustomSelectOption countryOption = new CustomSelectOption();
            countryOption.label = customShippingRecord.Country__c;
            countryOption.value = customShippingRecord.Countrycode__c;
            countryOptions.add(countryOption);
        }

        CustomSelectOption provinceSelectOption = new CustomSelectOption();
        provinceSelectOption.label = customShippingRecord.State__c;
        provinceSelectOption.value = customShippingRecord.Sattecode__c;
        countryProvinceMap.get(customShippingRecord.Countrycode__c).add(provinceSelectOption);
    }
    
    returnMap.put('countryProvinceMap', countryProvinceMap);
    returnMap.put('countryOptions', countryOptions);
    return returnMap;
}