How to C3850 upgrades from BUNDLE mode to install mode

[haininghuang3185]

I have two C3850 switches, in stacking mode. The current ISO version is 16.3.6, BUNDLE mode, and I need to upgrade to 16.6.9 version install mode. How can I do this?
1. Do I need to switch from 16.3.6 BUNDLE mode to install mode and then upgrade to 16.6.9?
2. Can I upgrade directly from 16.3.6 BUNDLE mode to 16.6.9 install mode?
3. In addition, I would like to ask if I can upgrade each device one by one in a stacking network, so that it will not affect the existing network services.

[Kasun Bandara]

Hello @haininghuang3185 

follow below guides. video have practical example.

https://www.youtube.com/watch?v=osGrRDQtJ9c

https://community.cisco.com/t5/networking-knowledge-base/3850-switch-ios-xe-upgrade-detailed-standalone/ta-p/3138609

[Leo Laohoo]

Cisco 3850: IOS-XE/Firmware Upgrade