Dell XPS 15 9570 - Upgrading SSD to PCIe Gen4

Hi all,

here's my laptop's details:

Memory: 16 GB
Processor: Intel(R) Core(TM) i7-8750H CPU @ 2.20GHz[Cores 6] [Logical processors 12]

Baseboard (motherboard): 0D0T05 - SN: /G1JCPV2/CNCMK0094U0560/

I want to upgrade the SSD and would like to know if this model supports PCIe Gen 4 or just Gen 3.

I searched online but got mixed info.

thank you!