You'll have to export it as either MD2 or B3D format. 3dsmax doesn't do either unfortunately.
There is a Halflife SMD exporter somewhere for 3dsmax. So export to that, load into Milkshape, then export as MD2 or B3D.
There is a Halflife SMD exporter somewhere for 3dsmax. So export to that, load into Milkshape, then export as MD2 or B3D.