vb.org Archive - Migrating subcategories from one server to other

I am facing a problem where a huge forum of mine should be divided into little pieces and migrated separately discussion by discussion.
We have more than 1 000 000 post and 105 000 user and so on.
The forum hierarchy is something like that scaled with 30 :D

Project group

Project 1

General Discussions

BlaBla Discussions

Project 2

General Discussions

BlaBla Discussions

Project 3

Project group 1

Project 1

Project 2

And so on.
All Project has its own theme with custom project logos, backgrounds, etc.

I was requested to move everything, posts, threads, users, userides project by project, VB 3.8.2 to VB 4.1.11.

Do you have any pointer, script, how-to or any info?
Is it possible to divide my forum into little chucks of data and migrate to a new instance?

Any help would be much appreciated.
Thank you

X vBulletin 3.8.12 by vBS Debug Information
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X vBulletin 3.8.12 by vBS Debug Information

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Hooks Called:

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X vBulletin 3.8.12 by vBS Debug Information
Page Generation 0.01147 seconds Memory Usage 1,703KB Queries Executed 10 (?)
More Information
Template Usage: (1)ad_footer_end (1)ad_footer_start (1)ad_header_end (1)ad_header_logo (1)ad_navbar_below (1)footer (1)gobutton (1)header (1)headinclude (6)option (1)post_thanks_navbar_search (1)printthread (1)printthreadbit (1)spacer_close (1)spacer_open Phrase Groups Available: global postbit showthread	Included Files: ./printthread.php ./global.php ./includes/init.php ./includes/class_core.php ./includes/config.php ./includes/functions.php ./includes/class_hook.php ./includes/modsystem_functions.php ./includes/class_bbcode_alt.php ./includes/class_bbcode.php ./includes/functions_bigthree.php Hooks Called: init_startup init_startup_session_setup_start init_startup_session_setup_complete cache_permissions fetch_threadinfo_query fetch_threadinfo fetch_foruminfo style_fetch cache_templates global_start parse_templates global_setup_complete printthread_start bbcode_fetch_tags bbcode_create bbcode_parse_start bbcode_parse_complete_precache bbcode_parse_complete printthread_post printthread_complete
Messages: