Hello, I can't find AP3 now 5.3 firmware, do you have it?

ArduCopter Copter 3.5
1

There is no firmware on the official website. Thank you.

2

Do you mean ArduCopter 3.5.x?
ArduCopter 3.5.x does not exist. Only 3.4.x and 3.6.x and both are outdated, please update to ArduCopter 4.1.5

If you do not want to do it, here are the available ArduCopter firmware versions