The xDBC folder is on your installation CD or in the folder where the files you downloaded were unzipped.
HOWEVER: if you downloaded and installed the trial version, you get no ODBC drivers. You can download trial ODBC drivers from www.DataDirect.com/ODBC.
WIth the trial version of FileMaker, I had no ODBC drivers in my download, and the link www.DataDirect.com/ODBC resulted in "File not found"
I had to download and install a trial version of SequeLink from the DataDirect site and now I have the needed drivers.