From a local install (flash drive) to a solid state drive, not very long -- should be under 30 minutes. If you're using a hard drive, longer. And if you're using an Internet connection (Dell recovery, etc.) it's completely dependent upon your connection speed and the quality of connection -- and on server load at Dell.  
Reinstall Windows for Vostro 3490. How long does normally take?  
Vostro 3490