The following code can be used to conditionally change the default value in a field, depending on a parameter in the URL. Change 25, 26, and 27 to your field IDs. Replace 'pass_entry' (in two places) with the parameter name in your URL.

This code will get the text value from a Dynamic field and copy it over to a second field. Replace 125 with the ID of the field to change and replace 120 with the ID of the Dynamic field to copy. If you want to copy the value from a Dynamic list field, change 20 to the ID of the Dynamic field that the Dynamic List field depends on. Replace 50 with the ID of the linked field that the Dynamic field loads entries from.