Not sure what you mean by "upgrade path", but logistically 3.x does require paying for new license(s). FWIW, I migrated directly from 2.6 to 3.1, bypassing 3.0 and 3.0.1.
The documentation you're looking for is probably something along the lines of "Data Migration Guide for LAN Management Solution 3.1", which lists topics such as "LMS 2.6 or LMS 2.6 Service Pack (SP1) to LMS 3.1":
I'm working on a project that includes basic router configurations. I configurated everything including: line console 0, line vty 0 15 and secret passwords. There are 3 routers in the network and every LAN is going t...
Desire to create Terminal Server ("TS" in this document) out of 2811 Cisco Router with HWIC-16A card (with Octal cables)
Desire to use SSH over Telnet
TS is ip'ed, SSH access configured (to the TS)
Python based Script to BULK Import/Delete devices using Cisco Prime API
Check my Repo on GitHub for all the details ( see below link )