a) the SSD won't have a bootable partition
b) the system registry doesn't get copied
I've migrated 2 different systems, and it's been effortless...as long as the SSD is big enough. I've used external drives, when needed, to off-load music and other large sections off the original system disk.
MIgration software will look for your system drive...C. That's the one it'll use as the source, and it won't touch the D drive. (Altho it might give you the option to copy over those folders.) There isn't any need; once you've done the migration, and set up the SSD as your boot device, you can copy the stuff on the D drive manually later, or just leave it as it is. You'll want to copy if you want to change the partitioning on the hard drive, for example to make it one larger drive.
To do what you seek, you cannot do it by whatever you said above.
You can't just 'copy'.
You have two options to use the new SSD as the main boot drive:
1. Clean install on the SSD
2. Migrate from the existing HDD to the new SSD.
For option 2, there are a couple of considerations first:
A. How large is the new SSD, and B. how much total used space is on the existing HDD?
If A is smaller than B, it won't work.
it's a 250GB SSD, but my HDD is splitted into a C and a D platform.
But if I take both of them, I still got only a 150GB on my HDD
OK then. You may be a candidate for a migration.
Acronis Trueimage, Casper, Easus Todo, Macrium Reflect, the included software with a Samsung drive...
Any of those will take the entire contents of your C drive and move it to the new SSD.
When you do it, follow the directions closely, and understand what is happening before you click.