I want to upgrade the SSD of my laptop Need some help with

How to Install an NVMe SSD In a Laptop – DIY in 5 Ep 113 nvme m 2 slot laptop Interface Form Factor: · SATA · SATA · NVMe PCIe · NVMe PCIe · NVMe PCIe · PCIe · JetDrive · Type-C nvme m2 slot motherboard 2 drive My astonishment came when i saw there is no screw or holder of any kind to fix the drive Please see the picture of the 2nd slot

nvme m2 ssd slot In the market there are NVMe ssd with various capacity How do I know what is the maximum capacity for my laptop My present Hard