Can I upgrade my HP Pavilion x360 ssd?

[NewUser15]

In the above pic there is this black box in the ssd slot. Currently I have the below storage :

With what type of ssd card can I upgrade my pc? Can I remove the black box and put a SSD card there? Or is it that I cannot upgrade my laptop with any ssd or HDD?

[Huffer]

You have an SSD now. I have marked up your picture:

red oval green rectangle purple star

The red oval is your existing SSD. It is an M.2 SATA 256 gigs. The green rectangle is the space where a 2.5 inch HDD or SSD can be located but you would need a special cable which would connect at the little purple star just to the left of the red oval, and a mounting caddy. In order to avoid having to hunt down the cable and caddy to add a 2.5 inch disk, I suggest you get a larger capacity M.2 SSD and place that in lieu of the one in the red oval. In order to be sure what kind of M.2 SSD you can add I need the full model number of the laptop. If possible you want to install what is called an NVME M.2 SSD; its a lot faster than a SATA but not all models will accept one. 

Post back with any more questions. 

[NewUser15]

my laptop model number is :14-cd1055cl. Which NVMe SSD can I use. Also, the black box is so strongly fixed to the base I am wondering how can I remove it. My another question is, if I replace the existing ssd with larger capacity one as suggested by you, I will lose the operating system which I do not want to. So I think I need to use 2.5 inch SSD disk.

[Huffer]

You will not lose the OS. There is a license for Windows 10 (assuming you bought the laptop with Windows 10) embedded in the BIOS and you can reinstall onto a new storage drive. HP provides backup software and you can make a thumb drive to reinstall a factory image or you can clone the existing installation to a new disk. The black box is a piece of foam rubber and can be removed with a box cutter or other sharp tool.  

[FairyTalePink]

If you decide to stick with NVMe, I recommend this one:

https://www.amazon.com/gp/product/B08DKB5LWY/

The SK Hynix Gold P31 is known for its performance to watt ratio, making it an excellent choice for laptops. I just got one installed in my Pavilion 15-eh0095nr. I ran CrystalDiskMark and it performs as advertised in my laptop, and I can actually notice a difference in speed vs. the original SSD.