Parallels 15 licence for Parallels 13 ?

Hello everybody,
I'm using a software that works only on yosemite maximum.
I don't mind staying on Yosemite as the software is a complete solution and contains everything I need.
However, there is one specific thing I can't do and that needs Sierra minimum, but it's not a main thing.
That's why I want to stay on Yosemite and run Sierra via Parallels just for this specific task.

Yosemite accepts only Parallels 13.
I installed the demo version of Parallels 13 yesterday and it works exactly has expected, it's perfect.

I would like to buy a Parallels 13 licence.
Therefore, my question is : Where do I buy a parallels 13 licence ? If I buy a Parallels 15 licence will be work Parallels 13 ?

Thank you for your help.
Edmon.

 

@edmon Parallels Online Store only offers the latest version of Parallels Desktop. Thus, if you would like to buy any of the previous versions, please check if it is offered by your local resellers or authorized online resellers like Apple, Amazon etc.