As of now June 2021 Apple hasn't released a patch to allow their M1 Laptops use more than 1 external monitor. Luckily there are workarounds made for this. I'd recommend checking to see whether this is patched first to save the money as you will need an expensive adapter.
we used the following:
Other than that you just need the DisplayLink Manager software which can be found here and then its just plug and play: