Spoke replacement: Mavic 26" D321 36 spoke with Shimano Deore XT FH-M576

[Sramcialized]

Looking for help locating a spoke for a Mavic 26" D321 36 spoke disc rim. It has a Shimano Deore XT FH-M576 hub.

I did contact Mavic but they pointed me to the calculator that wasn't quite clear how to use. Can someone kindly either indicate the spoke length needed or provide some guidance on how to use one of the known online calculators? I really don't have a ruler on hand to measure anything, so I am requesting if someone can help determine spoke length from the given information.

Greatly appreciated. This will get me back on the road.

 

[Ajax Bay]

Measure the old one, or take an intact one out (from the same side) and measure it.
Way quicker and far more reliable. Though will require one of those 'ruler' things. If in doubt go shorter not longer.
You'll be wanting double butted.
At your risk (and thank you for including all the info needed in the OP! Unusual):
https://spokelengthcalculator.com/
Left Spoke Length:256mm
Right Spoke Length:254mm

Mavic 26" D321 36 spoke disc rim. It has a Shimano Deore XT FH-M576 hub

Notwithstanding this, I would take one out and measure. Given you have tubeless on there, just undo (will need a spoke key obv) and that way the tyre can stay on. You can measure it leaving the spoke in its 'ole in the rim, so the cassette can stay put.