Cow, that won't work, it has to be a URL...
http://blah blah
The quotes are only a tiny bit, if at all, of your challenge.
The console is tricky in and of itself, as colon (

means "start new command on same line".
So, typing say hello : say world in console would end up you saying in chat
<you>: hello
<you>: world
Try, with no guarantees from me;
bind 9 "ulx playurlsound http\://monicasnwo.site.nfoservers.com/server/music/swag.mp3"
That extra \ in front of the colon is an escape sequences in lua, I forget if they work exact same way in Source console.
Escape sequences tell code to not 'interpret' the next character as it normally would.
I forget what can be used in console.