Your 2D drawing can be used to construct your 3D model. What is your pump system comprised of parts-wise? Is piping involved or is it just the pump itself? What type of pump?
Some of the 3D commands you would be using are extrude, union, subtract, as well as slice, separate, and move faces. Do you anticipate the use of any surfaces? If so, commands such as revsurf or edgesurf would come in handy.
You'll also have to become acquainted with some of the settings that affect 3D display. There is a lot to learn. Don't dispare however. There are plenty of knowledgeable and helpful people here at CT to assist.