Why are you asking here?
The best resource for finding open-source software is an internet search engine.
Have you searched for
7 level formatting or
35 level formatting?
I suspect that you have and couldn't find anything. That's because, AFAIK there's no such animal. I am of course willing to be proved wrong.
By any chance did you mean 7 pass or 35 pass wiping?
Take a look at
DBAN (Darik's Boot And Nuke)[
^].
BTW: Unless you are writing something for a government organization that insists on this, more than 1 wipe followed by a write of all zeros is generally unnecessary.