I understand that you want to convert your Perpetual license to subscription model. I would like to inform you that, since both the products are from different segments to these cant be converted .
What you can do in this case is return your perpetual license to your reseller and make a new purchase for subscription using the below link.
1 person found this helpful
No it is not possible to get any money back.
But the 2 versions are exactly the same as to the downloaded install file and alll the files installed on your system.
The difference comes from what Adobe ID you use to Sign In with.
So it is possible to convert LR 6 into the the subscription base version LR CC 2015. All you have to do is buy a photographers plan subscription, and you can use the same Adobe ID to do that, and once that subscription becomes active, which should be almost automatic, you Sign Out then Sign back in. \
You should also download and install the CC Desktop App so you can install Photoshop. Once signed in on the CC DTA your current install of LR should change from the 6 version to the CC version.