Hi,
Have a look at the release notes for 16.05 for the changes when upgrading to 16.05 from previous releases.
http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-5/release_notes/ol-16-5-3850.html
The "software install file" has been replaced with "request platform software package". The 3850 in install mode boots from the package file. When you upgrade the code it will point the switch to boot from the new package file. The old .pkg file for release 3.3.5 will remain in flash so that you can rollback the code. You can clear the old code from flash using the "request platform software package clean" command.
Hope this helps
Thanks
John
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