In order to get the Umbraco nodes which use a certain umbraco Document Type, you can use the following SQL script. You can then simply login to umbraco backoffice and search for the nodeId value in there and find the node that you want.
SELECT * FROM cmsContent C
INNER JOIN cmsContentType CT ON C.contentType = CT.nodeId
INNER JOIN umbracoNode N ON C.nodeId = N.idWHERE CT.alias = 'YourDocumentTypeAlias'