Morph codes can be hard to find sometimes, but an easy and simple way to find them is this. If you are a <GM> or admin on your server, spawn or select any npc in the game and type: .npc info
Everything about the creature will be there, including a display ID which can be used in the .morph function. Hope this helps! I know it helped me.
Also if you want a specific morph code, look up the NPC on your favorite WoW database( Thottbot, wowhead, allakazam ect.) and look for the last numbers at the end of the web adress. That is the spawn number, spawn it in game, .npc info it and then you have the morph code for it! Tell me if you need any more help on private servers - Shiny