To get Dark_AleX firmware, you need to downgrade to 1.50; The highest downgrader available is for 3.03, not 3.10. Trust me, you will brick your psp if you try to use the 3.03 downgrader on a 3.10.
I am a member that dominantly posts the member/homepage news, so you can check up on use regularly, and you will be one of the first to know when the dowgrader for 3.10 or above is released.
The team that creates downgraders and such, is a team called noobz. You can access their website
here.
Just as a warning, there is no talk on illegal game talk (ISO/CSO) allowed on PSP3D; you may get banned if you do so repeatedly.