SELECT o.[Order], o.Product, o.qtyOrd, oh.[Date], P.MinQty

FROM ORDDET O

INNER JOIN ORDHEAD OH ON OH.[Order] = O.[Order]

LEFT JOIN (SELECT o.Product, MIN(o.[Order]) MinOrder

FROM ORDDET O

GROUP BY o.Product

) mino ON mino.MinOrder = o.[Order]

LEFT JOIN PRODUCT P ON P.Product = o.Product AND p.Product = mino.Product

There's probably more performance-friendly ways to do it, but this should get you started.