Madmax is an external program that one can compile from source.
The stotiks place at github has an already-compiled version for Windows.
It hasn’t been updated in a while, so K=32 is the highest for that one.
Chia since v 1.2.11 comes bundled with Madmax (and Bladebit), and supports higher K.
But:
If you use the “chia plotters madmax (…)” please note some arguments don’t work as they are intended: -w, -G -2, -t and -d
It was fixed a few days after 1.2.11 was released. https://github.com/Chia-Network/chia-blockchain/pull/9197
If you use chia_plot.exe directly (in other words not the “chia plotters madmax (…)”) you should be fine.
I haven’t used Madmax to create higher-valued K files, so can’t help you with that.