If you would like to see which contacts in a group are on your suppression list you can export both as CSV files, sort each spreadsheet in alphabetical order and then paste one alongside the other to see those on your suppression list.
To export a group as CSV:
Go to Contacts and click on the Groups tab.
Click View on the group you wish to export.
Click the grey Export to CSV button - the download will begin automatically.
To export your suppression list:
Go to Email and click on the Suppression List tab.
Click the grey Export to CSV button - the download will begin automatically.