FBA tax, duties, tariffs

Hello everyone.

I already did my bulk order it’s about to ship to the Amazon warehouse now. I am a little confused now. When do I have to pay import tax (duties, tariffs) ? Should I wait until my product reaches to Amazon fulfillment center?

And I asked my supplier about hs code today, when she sent that to me I want to check on website how much I have to pay for it but I could not find website that I can check. I found

https://www.tariffinder.ca/en/getStarted this website which looks like Canadian tarff calculator but could not find China from list of country.

Is there anything I am missing or misunderstood?

Thank you .