The adapter is the VESA 100x100, the monitor already comes with it.
But you don't need the triple stand, the monitor is only attached to the centre one.
This is sufficient Oplite GTR ELITE Single Monitor Stand

Hello, this stand is designed for 3 screens up to 32".
For a single curved screen, this product will be more than sufficient Oplite GTR ELITE Single monitor stand
However, if you want 3 g9 screens, you'll have to find another solution.

Oplite have an one arm monitor stand, look Oplite GTR ELITE Support pour moniteur unique instead

One can, but three cannot.