The nonprofit/fundraiser identifier is the number (3+ digits) in the last part of the website address of the nonprofit or fundraiser profile. It is also sometimes referred to as the "social entity number" or SEN.
You can find this number by searching for a nonprofit or fundraiser on ammado.com and clicking the # symbol at the top right of the profile page.
Here you can see the # symbol located below the Moderator.
Clicking the # symbol will change the URL in the address bar from, say, https://www.ammado.com/nonprofit/ifc to https://www.ammado.com/nonprofit/120482. The nonprofit number in this case would therefore be 120482.