this is the code for the component: 

getAttachements: function(component) {
        var plantId = 'a0F0Y000005c7DcUAI';
        var action = component.get('c.getContractAttachedUrl');
        action.setParams({
            "plantId": plantId
        });


        action.setCallback(this, function(response) {
            var state = response.getState();
            if (state === "SUCCESS") {
                var urls = response.getReturnValue();
                component.set('v.slides', urls);
            }
        });

        $A.enqueueAction(action);
    },

and this is my apex class: 

@AuraEnabled
    public static  List<CombinedAttachment> getContractAttachedUrl(String plantId){
        
        // Get Contract Id from plant
        Date now = date.today();
        Entity_Contract_Relationship__c contractId = [Select Contract__c from Entity_Contract_Relationship__c  where Entity__c = :plantId and (Valid_to__c > :now or Valid_to__c =null) limit 1];
        
        // Get Attached Files
        List<Contract__c> RepCombinedAttachment = new List<Contract__c>();
        List<CombinedAttachment> RepComAttachment = new List<CombinedAttachment>();
        RepCombinedAttachment = [Select (Select id, title,contentUrl, LastModifiedDate, createdby.name,RecordType From CombinedAttachments) from Contract__c where id = :contractId.Contract__c];
        for(Contract__c  cc: RepCombinedAttachment){
             if(!cc.CombinedAttachments.isEmpty()) {
                 for(CombinedAttachment temp : cc.CombinedAttachments){
                     RepComAttachment.add(temp);
                 }
             }
        }
        return RepComAttachment;
    }