I have a floor furnace that is old made by Mahl MFG. Model is the Warmahl 50x.

The hourly input is 50,000 BTU and the hourly output is 35,000 BTU.

How do I light the pilot can not find instructions any where.

You need to find the pilot & the gas valve.
Turn the knob on the gas valve to "pilot".
Either that knob or a button next to the knob will need to be pushed down (like you are trying to push it into the valve body) & held while you light the pilot.
Once the pilot is lit, hold the button or knob down for at least 30 seconds then release. The pilot should stay lit.
If it does, turn the knob to the "on" position.