This site is not for solicitation of services or 'purchasing' development. Please do not post requesting side mods/plugins and so on. Your thread will be removed, and you will receive a warning.
EDIT: I do see on your account that you have linked your MC Account. Not sure if you did that after the post or before.
Anyway you should just be able to enter the command now.
Best of luck to you.
Also, will everyone running pixelmon be able to see the hat? And do I have to input the command on a pixelmon server or does a single player world work too?