Closing multiple contour lines with z-height and preparing for

I can’t figure out how to solve this: 1 I want to close all of my contour lines with different heights (z-value) (main question). 2 Lay them out on the world plane, making them ready for laser cutter, maybe numbering them - the most efficient way?

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5.5 Contour Lines and Intervals

5.5 Contour Lines and Intervals

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5.5 Contour Lines and Intervals

Contour line - Wikipedia