22 years ago Velux required a sloped curb on slopes less than 5/12. 10-12 years ago they improved the glazing system and lowered that to like 3/12. 7-8 years ago they eliminated the sloped curb assembly. There will not be a Velux flashing kit for that curb and any sort of metal roofing. You need a new roof cover and a new curb mounted skylight. I put a deck mount solar powered venting skylight on my brothers house, 3/12 pitch, corrugated steel roof, Velux metal roof flashing kit. It leaked like a seive. To fix it I had to remove all the steel top to bottom, fill between the purlins with extruded foam insulation, and cover the whole thing with ice and water, 8 feet wide and just over 3 square in area for a light approximately 20x40 inches.