cd4059a

I'm having trouble understanding the data sheet for a 4059a divide by n chip
I need to divide the input by 1000. I can't figureout which pins to jam.
thankyou for your time

There are a few ways of doing it. The datasheet shows how to calculate the values starting at page 4-6:
https://www.electro-tech-online.com/custompdfs/2008/07/cd4059a.pdf
So if you use "mode 10" then the jam numbers would be BCD 1000 applied to the Jam 16 - 1 inputs. Jam16 is the most significant bit and Jam1 the least. Ka & Kb would be high and Kc would be low for "mode 10". This chip seems to be easier to understand when in "mode 10". If you use the other "modes" the digits get mixed up a bit and it gets confusing without drawing it out on paper. There may be an advantage to using "mode 8" due to the fact that the last counter would be in divide by 2 mode giving you 50% duty cycle output in theory but the datasheet isn't 100% clear on that.
If you use "mode 8" then the jam numbers would be BCD 1250 applied to the Jam 16 - 1 inputs. Jam16 is the most significant bit and Jam1 the least. Ka & Kb would be low and Kc would be high for "mode 8".