I am not sure if it always look the same, but if you log in to:
https://my.wmtransfer.com/login.aspx?l=en-USyou see your registered emailaddress on the top followed by the line PURSE:
here you see all your purses (different currencies - what you need is WMZ, if not already available klick on the plus-sign in the same line to create one)
open the WMZ-puse, you see first line the actual balance and in the 2nd line named NUMBER: the number of your puse starting with the letter Z (you need to enter this letter also into exwp-website)