smounche :
I don't need to change the drives.
the new SSD will be Drive C:
And the old one - will be drive D: for data.
only one drive with an operation system on it - the SSD with win 10.
what is the process i need to do to have an activated win 10 on the machine ?
Yes you will be changing drives.
Your current C is on the HDD?
And you want an SSD for the C drive?
So...upgrade your current Win 7 to Win 10.
Once activated, this means that your system has a digital license for Win 10.
Then, you can change drives, and either clean install on teh SSD, or clone from the old drive to the new SSD.
To "upgrade to Win 10"
Create a Win 10 USB, here:
https://www.microsoft.com/en-us/software-download/windows10
Boot from that and run through the Upgrade process.
Hopefully, it will activate itself.
The official free upgrade period ran out long ago, but apparently it still works.
Once this system in its current state is Upgraded to Win 10 and activated...then you can get the OS on the SSD.