If you want to purchase CS6 it can be purchased thru the page linked below:
CS6 - http://helpx.adobe.com/x-productkb/policy-pricing/cs6-product-downloads.html
You can also use CS6 as part of your sunscription to the Creative Cloud.
If you want to get the trial version of CS6, you can download the trial version of the software thru the page linked below and then use your current serial number to activate it.
Be sure to follow the steps outlined in the Note: Very Important Instructions section on the download pages at this site and have cookies enabled in your browser or else the download will not work properly.
CS6: http://prodesigntools.com/adobe-cs6-direct-download-links.html