Assuming Jimitodd is correct, and I didn’t test but will be…
Heres how you can empirically determine the field id.
Use phpMyAdmin from your cpanel to look into the database. Locate the VFB Fields table, named wp_visual_form_builder_fields (note: the wp_ prefix is the prefix I chose for my DB tables prefix on initial build, yours may be different).
Once there you’ll notice there is a form_id column. Sort or filter to see the field list for the form id you’re working out.
Look through the field key until you find the field label you used in the form designer, then note the field_id for that field.
Now you can use {vfb-##} to display the desired field.