It's because Windows 10 is not supported on the N5010 (that is to say, Dell never released any Windows 8 or Windows 10 drivers for it). Only Windows Vista & Windows 7 are supported. Never change the OS on a laptop without first checking the driver situation on the manufacturer's website.
You have three options as I see it:
1) Revert to the OS it shipped with.
2) Buy a USB WiFi adapter.
3) Search the internet using Google to find a Windows 10 WiFi driver that works.
If I was in your shoes, and Windows 10 works fine on your laptop in every other respect, I would choose option 2.