Since you did so much of work to prepare this, you could've added some instructions or text tutorials to follow along which would've made it so much easier
From the top view, total breadth is 50 (30+10+10) and from 30mm of its ending side ,,, and from Front view at the middle of 60mm , You can find the required point and then draw from 20mm left and 20m right i.e. 40mm
