Okay, here are what you can migrate:
FireRed -> SoulSilver, Diamond, and Platinum
SoulSilver, Diamond, and Platinum -> Black and White
FireRed -> SoulSilver, Diamond, and Platinum migration
For this migration, you must use the Nintendo DS Lite or Nintendo DS, which has the Dual slot function.
Steps:
1. Insert the FireRed at the bottom, the SoulSilver/Diamond/Platinum into the top.
2. Turn the system on.
3. Select SoulSilver/Diamond/Platinum.
4. Start it up, but DO NOT start playing the game.
5. When you reach the menu, scroll down until you see: Migrate from FireRed.
6. Select "Migrate from FireRed."
7. Select "Yes" for all the questions asked.
8. Select 6 Pokemon that you want to transfer.
9. Select "Yes" when the game wants you to confirm.
10. After it is finished, start SoulSilver/Diamond/Platinum.
11. Continue playing the save file.
12. Fly to the Pal Park. (SoulSilver: Fuchsia City, Diamond/Platinum: Route 221)
13. Go inside.
14. Talk to the guy that looks like a worker. He will ask you if you want to be in a catching show. Select that option and he will give you 6 Park Balls.
15. Go through the areas and find your Pokemon. Different Pokemon appear in different locations. Also, you may need Surf to find some Pokemon.
16. After catching all 6 Pokemon, a bell will ring. You will exit.
17. The guy gives you a berry as a reward and put the Pokemon in the PC box.
18. Finished!
However, there are requirements for both games before you can transfer.
FireRed: You must have at least 7 Pokemon: 1 in your party, 6 in the box for migration.
SoulSilver/Diamond/Platinum: Beat the Elite Four, obtain National Pokedex.
Also, there are requirements for the Pokemon: They CANNOT have HM moves from the game. (Cut, Fly, etc)
Also, you have to wait 24 hours per migration.
SoulSilver, Diamond, and Platinum -> Black and White
For this one, you need 2 DS's. Perfect. That's what you have.
Steps
A. Insert a SoulSilver/Diamond/Platinum in one DS, and a Black/White in the other.
B. Turn the DS with Black/White on.
C. Start the game.
D. Fly to the Poke Transfer lab at Route 15
E. Talk the the guy in the center, all the way up the stairs.
F. He will start up Poke Transfer after a save.
G. Turn on the DS with SoulSilver/Diamond/Platinum.
H. DO NOT START THE GAME. Just stay where it has the selection of your game.
I. The DS with Black/White will give you the instruction: DS download play.
J. Select "DS Download Play from the the DS screen of the DS that has SoulSilver/Diamond/Platinum.
K. The software will download.
L. Then, the DS with SoulSilver/Diamond/Platinum will ask you to select 6 Pokemon to migrate.
M. On the DS with SoulSilver/Diamond/Platinum will now tell you to play a minigame. Play it. If you want to see the minigame, see http://www.youtube.com/watch?v=TA1DHdli-bI
N. The game will ask you to confirm. Confirm it.
O. Wait for the game to save it.
P. Now the DS with SoulSilver/Diamond/Platinum will ask you if you want to tranfer again. If you want to, say yes, if not, say no.
Q. If you said yes, repeat steps L-P. If no, then the DS with SoulSilver/Diamond/Platinum will ask you to shut off the DS, while the DS with Black and White will exit Poke Transfer.
R. He will then Box your Pokemon.
S. Finished!
Again, there are requirements for both games before you can transfer.
SoulSilver/Diamond/Platinum: You must have at least 7 Pokemon: 1 in your party, 6 in the box for migration.
Black/White: Beat the Elite Four, obtain National Pokedex.
Also, there are requirements for the Pokemon: They CANNOT have HM moves from the game (Cut, Fly, etc) and they cannot be holding items.
You can do this as many times as you want until you run out of Pokemon.
If you want to transfer from FireRed to Black/White, Follow steps 1-S.
Hope this helps!