I need help solving this problem in solidworks step by step

1st Step: Start by making the top view section taking the basic measurements.
2nd Step Lift the part to maximum measurement with extrusion.
3rd Step: Use the cutting feature to cut the 1st section of the 3 sections (1st section is the 35 x35 square), thus achieving the shape of the 1st section
4th step: In the side view, sketch the triangle design with the circular radius, and draw a line at the ends.
5th Step: make the cut to the given point of the 3rd section to obtain the shape of the triangle with circumference.

NOTE: I couldn't understand the 1st section because I can't see what the 10mm of it would be. Needed more details about this drawing

Best way to learn is Try It Yourself. There are many ways to model this part, here is one of them.

Hope it helps, it's best if you can try it yourself