How urgent is your need for a solution? It's relevant because no one has replied yet (the most knowledgeable are a day behind me).
If you need a solution now - upgrade plugin may not work because you are wanting to upgrade 8 year worth of DokuWiki, template, and plugins in one hit. That's a hell of a lot to expect an upgrade mechanism to deal with! (I'm guessing).
My suggestion, in lieu of better input, is to:-
1. backup everything you currently have.
Do not modify your production server until completely happy with proven results.
Do not modify your backup of the production server -
work only with copies. Post again
if, after careful consideration and some research, you have
any concerns about how to setup a development server - please include information about the OS and it's environment that you normally use (i.e. your home computer). If you are at all uncertain, after
reading the documentation on the main DokuWiki site please post more information about your production DokuWiki environment (OS, type, access restrictions, etc) to this thread and someone will provide instructions.
2. copy the backup to a development server, then,
on the development server (by definition, not available to anyone but who your authorise):-
3. note what has been previously, modified/hacked (back up those modifications separately)
3a. disable as many plugins as possible (
for blah in $space_separated_list_of_plugins;mv $DokuWiki/lib/plugins/$blah $somewhere{,.bak};done) (only applies if you have root access and it's a Linux server)
3b. download and extract the latest DokuWiki to your development DokuWiki - replace
everything (First set things to the DokuWiki current model, then attempt modifying it to match any modification made eight years ago - some hacks/changes may no longer be relevant/workable/necessary).
3c. download and extract the latest DokuWiki template to your development DokuWiki -
replace everything
3d. incrementally install the latest plugins to match your previous (8yo) plugins. After
each single plugin is upgraded/installed, test the site
before proceeding to the next plugin installation/upgrade.
3e incrementally install the previous (8yo) modifications/hacks over the latest installation.
3f. test, review, test, rinse and repeat until happy
4. after all tests prove your upgraded DokuWiki is working perfectly - replace your production DokuWiki with the development version and try not to let more than two years pass before attempting another upgrade. :)
Your feedback is appreciated (I could learn valuable lessons from your experience).