Venu,
Make sure before you export TN profile in 6.1,that particular ExternalID type(DUNS Plus Suffix,SCAC,Phone etc…) exists in TN DB.If not install that missing ID from the ISAdmin/WmEDIforTN Add EDI ID Types section.
So this could be reason TN6.1 is throwing unknown ExternalID typecode while importing the profile.
HTH,
RMG>