Go to the Meeting Place and talk to Cranidos if you haven't opened that gate already and go through
He is in the beach zone
the cavern zone
He is in the granite zone in the room where you battled electivire.
haunted zone
in the volcano zone
Shroomish is in a crate in the meadow zone. It's close to where you find Magikarp.
They all should be in that zone.
In the Beach Zone ,not that close to the Drifblim Stop
By the water
The magma zone
In the flower zone go to the driblim stop then dash beyond him to find the bouquet.
If you mean phanaphy he is in the cavern zone after u become friends with snorlax