Inspiron 3531, Windows 8.1 factory recovery problem

Hi,

I have to make a factory recovery because after installing Windows 10, the laptop slowed down extremely. Rollback is not possible? I am not able to make the recovery. It will be installed the Windows 10 instead of original Windows 8.1. I tried the recovery tool, but it says for this service tag (recognized automatically) that I cannot download the image. I don't now what to do! How can I reach the original factory recovery partition to set up the factory installation?