You can not catch it in leafgreen,but in firered you can.
You can catch Mareep in Altering Cave.Mareep is not available in firered you must trade one from emerald or colosseum.
You'll need to trade for it.
The only way you can get an ampharos is to catch a mareep then level it up to level 30. You can catch a mareep on Route 32, 42 or 43. Good luck ^^
You can only get a Mareep by using a Wonder Card which is used in Mystery Gift and with the Wireless Adapter that alters the Pokemon inside Altering Cave allowing you to catch a Mareep, Teddiursa, Houndour, Stantler, Pineco, and Zubat (Which is the only Pokemon you can catch without Mystery Gift.).
You can either catch a mareep, breed a mareep, trade a mareep or go to the global trade station and ask 4 a mareep/ Ampharos :)
catch a mareep and train it
you can't
You can not catch it in leafgreen,but in firered you can.
The Kanto or Johto region.
trade
Nowhere.
trade him
you can catch mareep in vallyworks using the pokeradarmareep is by floaroma city, in the grass by the valleyworks. use a pokéradar, and if the grass is shaking, and is shining, go into that patch of grass, because it's more likely mareep is there. mareep isn't hard to find, but will only be a level 6-10. Mareep is easy to catch aswell. Hoped i helped:P pokefan_booo
You can't catch Flaafy, but you can catch Mareep at the Valley Windworks.
You can catch Mareep in Altering Cave.Mareep is not available in firered you must trade one from emerald or colosseum.
easy catch a mareep