Basically the title, you need to use the skills you have now and be a productive member of society.
I don’t mean go back and show the wheel or try invent germ theory etc.
For example I’m a mechanic i think I could go back to the late 1800s and still fix and repair engines and steam engines.
Maybe even take that knowledge further back and work on the first industrial machines in the late 1700s but that’s about it.
I’d have to re-remember a lot of stuff I’ve forgotten, but late 70s, early 80s.
Unless you count “typing” as a marketable skill, then I could probably go back to 1872?
You probably type too fast for the old typewriters and don’t hit hard enough, but you’d adapt. And don’t forget the carriage return!