Sorry, my bad typing.
It has a 256GB M.2 SSD and has One M.2 2280 PCIe® 3.0 x4 slot.
I want to replace it with a 2TB.
OK...
DO you have some other drive or storage location, with enough free space to hold the entirety of your current OS drive?
(this is NOT a clone, just needs the free space)
1x m.2 slot with an Image
Assuming you have another drive (any type of drive) with sufficient free space to hold the entirety of your current m.2 drive:
1. Download and install
Macrium Reflect
2. Run that, and create a Rescue CD or USB (you'll use this later). "Other Tasks". Create this on a small USB flash drive or DVD.
3. In the Macrium client, create an Image to some other drive. External USB HDD, maybe. Select all partitions. This results in a file of xxxx.mrimage
4. When done, power OFF.
5. Swap the 2 drives
6. Boot up from the Rescue USB you created earlier.
7. Restore (on the toolbar), and tell it where the Image is that you created in step 3, and which drive to apply it to...the new m.2
8. Go, and wait until it finishes.
9. That's all...this should work.