Windows 8 reinstall without recovery partitions

Hello,

I had Windows 8 and Linux installed on my Inspiron 15 7537, with dual boot, all worked perfectly for months. Yesterday I had to reinstall Linux and during the procedure all the partitions of my hard drive have been deleted by mistake. :emotion-3:
Now only Linux is working and I also lost the recovery partitions.

I have a factory backup made with Dell Backup and Recovery on an external hard drive, but I don't know how to use it. I'm not able to boot the PC from that... Any solution?

Thank you

Loris