The link to the OKTech plugin for 1.9 web services ended with this:
"This will be done at the pace of an old man, two years away from retirement and extremely busy with his two grand-children "
and that was how long ago?
What's your timeline for accomplishing this?
And ... hyper-jumping a 1.9.x backup to a 3.4.x (which is one version behind latest and greatest), me thinks will be interesting ... depending upon what mods/blocks/addons were used in ***each*** course as I think you'll have to address 'stuff' **one course at a time**
Think I'd do some testing prior to any programming ...
First, find the largest backup file in the 1.9. There's NO Moodle GUI tool for that I don't think ... you'll have to resort to command line guru stuff like ls -l moodledata/?????/backup/backup*.zip ... the ????? is the course ID number ... each course having a directory of it's own.
Once that is found ... xfer it or position it in a file system repo of the 3.4 where a teacher could see and use it.
Try that restore.
Second, find the course that has the largest number of Quizzes in it. For that you might have to use moosh or some guru MySQL query. Why Quiz? It's the heaviest when it comes to processing.
Try that restore.
Not trying to discourage, just know that what you are proposing would be a something that even Moodle Partners might not take on.
There ya have my 2 cent opinion .... how about any Moodle Partner here in community la-la-land? What say you?
'spirit of sharing', Ken