Zag0419,
Here is a link to the VersaLink B600_B610, VersaLink B605_B615 Paper and Paper Tray Specifications that has guidelines for the best print quality and to avoid jams. The gsm of the cardstock may be indicated on the paper packaging.
https://www.support.xerox.com/en-us/article/en/x_VLC500_en-O3759
I hope this helps.