Mod_rewrite help with rule

Hello, I need some pointers on how to translate incoming hits to some old URL's into different URL's. I know the basics of URL rewriting but am not too postive of how to convert something like :

mainsite.tld/Forum-Name/ThreadNumber-Thread-title.html

to

mainsite.tld/Thread-title-ThreadNumber/index.html

first is what I had, second is what I have now. any help is much appreciated.

EDIT * err on second thought maybe programing discussions was better suited for this.... Im sorry if I did post in the wrong section.

[Xplorer4x4]

I assume you are already using vRewrite
https://vborg.vbsupport.ru/showthread.php?t=104484

If so try this:
https://vborg.vbsupport.ru/showthread.php?t=112024