Downgrade to Firmware Version V3.5.1

Hardware Pixhawk family
1

Hi guys I want to downgrade to Pixhawk Firmware Version V3.5.1
I am having problems with the latest update I cannot find version 3.5.1
This version worked great for me can some body please give me a link as to exactly where I can download this.
This is the version I want from LogAnlyser

Vehicletype ArduCopter
Firmware Version V3.5.1
Firmware Hash 8ab1b3eb
Hardware Type

Thanks

2

Mabe you can search here: http://firmware.ardupilot.org/Copter/
You have to search for: Copter 3.5.1 31-July-2017 / 3.5.1-rc1 24-July-2017