I'm applying for a job as Structural drafter/designer using AutoCAD. The company is an engineering firm ?

Unless you have experience in the field, and it sounds like you don't, you will be responsible for working under supervision to learn about the systems. You won't start out designing stuff but doing work that is not that difficult. The important thing is that you are not expected to know much except how to use AutoCad and take instruction and ask questions when you don't fully understand what you are to do. You will be learning and at your level you need to really concentrate on doing what you are told to do and to ask questions about things you are unfamiliar with. My experience with people at your level is that the worst thing you can do is not ask questions about what you don't know.

You'll be doing structural and architectural drawings, floorplans, plan views, elevations, ducting, piping, etc.

Doug