Is there a way to do a global search if you only have an external ID? I was give the External ID but I don't know what search type to use to search all available tables. Thanks

There is no way via global search to search for any external id on a record.

You need to use a saved search with the External ID you have as the criteria. Problem here is you dont know what transaction type it is so you might just need to eliminate it one of one. Start with a transaction search perhaps, and then if not, entities next.

Perfect thanks