3 screens on D6000

[gregory_fr_44]

Hello,

Description my material:
- Dell xps 15
- Ubuntu 20.10
- Dock station D6000

I have 3 screens in addition to my laptop: Acer in vga/Dvi
on my D600 I have connected :

1- an hdmi<->dvi ( OK )

2 and 3- for the other two screens, I wanted to connect DP<->DVI but it doesn't work,

What is to be done?

Thank's