That will be;
cubic metre per sample = 1.5 x 0.15 x 0.025 = 0.005625 cu m.
so for 500 ---- 0.005625 x 500 = 2.8125 cu m.
All you have to do is decide how much you want to allow for wastage?
As it's hardwood, which is generally sold in cu ft that works out at;
~60 x 6 x 1 = 360cu in
x...