Will it work?

[SonnyNXiong]

If i buy an SSD can i just transfer all my w10 files and OS to the new ssd?
If i cannot do i need a new W10?

HDD-->SSD

 

[R3PLAY]

You can certainly do this. You will need some kind of migration tool, take a look at this tutorial:

https://www.digitaltrends.com/computing/how-to-move-windows-10-to-an-ssd/

If this was me, I'd just reinstall it. Most likely faster and less of a hassle than migrating between drives.


To answer your second question:

If you have a retail key: You will not need a new Windows key.
If you have an OEM key: You will not need a new Windows key, OEM keys bind to the motherboard.
If you upgraded to Windows 10: You will not need a new Windows key, it will be activated automatically when you install Windows.

 

[Eximo]

Yes, assuming the total space occupied on the hard drive is less than the capacity of the SSD. Most of the nicer SSDs, like Samsung's, come with a cloning utility, or access to a one-way cloning tool for use with their devices only.