All Unowns in SoulSilver are found in the basements of the Ruins of Alph.
You have to capture the first 26 Unown before getting the two other Unown.
by breeding two raichus
Yes mew two is on soul silver you just need to look in cereleun cave
Have ho oh and luck
You have two beat the Pokemon league.
catch nincada with two spaces in your party and a spare pokeball
Go to the goldenrod department store.
You need the Silver Wing and lots of any sort of Poke Ball.
Onix and Geodude are two I know.
cerulean cave after you beat all the gym leaders
Route two is Just Above Viridian City in Kanto.
you have to migrate it or have some one with soul silver or heart gold trade it to you