Upgrade from Build 8110

Upgrade from Build 8110

No one has done anything to our ServiceDesk Plus in regards to updates. I'm still running version 8.1.0 Build 8110. I know that you have to upgrade the version in order. What do I need to attempt to have our IT staff complete this? I have downloaded the 3 most recent versions, but I will assume that I am missing some and can;t go from 8110 directly to 9100.
Thanks

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