Variables inside a script

So, I’m using a PDF viewer and I need to set the URL that the plugin uses to get the PDF using variables from my queries

This happens (and doesn’t work), I’ve bassically leave between " the fixed part of the URL and the variables without any ":

image.png1384×408 95.9 KB

I’ve also tried all inside " (but it doesn’t work either):

image.png1384×408 89 KB

How can I solve it?