Firstly, congratulations on getting to the interview stage! I was in a very similar situation a few months ago, but mine is more of a cautionary tale. On the bright side, it was a learning experience.
I applied for a job I was almost totally unqualified for, and the interview consisted of me being extremely upfront and basically saying "I haven't done that before, but I have done [insert obliquely related reference here]". I got the job, to my surprise. One of the main reasons I got it was because I said I was willing to learn and be trained (but of course, I would expect that from every job). Adequate training was given for using the software and equipment, but not for anything else. Then after 3 months, I was told I wasn't working fast enough (with zero feedback before that), and then 6 weeks after that I was let go.
In hindsight, what I should have done when I started is ask for a more formal learning plan and feedback on my performance. I was aware of my deficiencies (i.e. not having a degree in mechanical engineering), so I could have broken that down and said "Ok, this week I'm going to spend time learning about electrical component design. I'm planning on reading these chapters from this textbook. Are there any other resources you recommend?" I'm not sure that would have helped me, as it might have been more of a personality conflict or something else behind the scenes. Also I was also doing so much learning the day at work that adding time after work would have been really draining. But I would have done it if it meant keeping my job!
In short, be completely honest in the interview, and ask them what sort of learning/training systems they have in place to ensure you succeed. If you aren't successful it's a great opportunity to say you really want that sort of position, and ask what you can do in the meantime to ensure you're successful next time.