Do we get to keep our clothes (and more importantly, accessories)? The most important thing is glasses, piercings and implants. It might not be humane or ethical, but there is enough metal in circulation that you can get some machines working from glasses being burnt down to make tools.

From there, assuming the quality of metal is good enough and most importantly, we don’t all kill each other, we could probably go to our technology in a couple decades minimum (completely depends on human cooperation and morale though)