Macbook Pro M1 Dual Monitors ?

[volleronline]

My laptop: Mackbook Pro M1 - 13 inch

Docking Station: Dell WD19

Monitors: Dell 24 Inch - S2421HS

My external monitors show the same mirrored display. It's extended but both displays show the same picture.

Laptop is open and display on laptop is fine.

One monitor is plugged into DisplayPort port.

One monitor is plugged into the back port next to the HDMI port (so, is that the thunderbolt port?) -- It is plugged into a secondary portable USB-C dock and from there connected to HDMI.

Am I plugging into the correct port? Do I need a cable that goes direct from thunderbolt/usb-c to HDMI?

Would really love to make use of both of these lovely monitors!

Thanks!