Getting trouble to send document to google drive File/Folder in Salesforce

Hi,

My requirement, I have Visualforce page where

1- I can attach a document and send to my google drive.

2- I can get all the folder from the google drive and show in VF page.

1st one I did successfully but in case of the 2nd point I am getting 'Forbidden' error.

Something I missed please guide me-

http objHttp = new http();
Google_Auth_Detail__c tmpGD = [select id,Access_Token__c,Authorization_Code__c,Client_Id__c,Secret_Code__c,Expire_In__c,Refresh_Token__c,Scope__c,Token_Type__c from Google_Auth_Detail__c limit 1];
Http http = new Http();
HttpRequest req = new HttpRequest();
req.setMethod('GET');
//req.setEndpoint('https://www.googleapis.com/drive/v2/files');
req.setEndpoint('https://www.googleapis.com/drive/v3/files/0B_QE5jslfxO6clpiRWRnOXpFR00?alt=media');
req.setHeader('Authorization',tmpGD.Access_Token__c );
//HttpResponse resp = http.send(req);
HttpResponse res;
res = objHttp.send(req);
system.debug(res.getStatusCode()+'......'+res.getStatus()+'....res.........'+res.getBody());

This is my method to get from google drive.