Try opening the files with text editor - the default dump format is plain text.
If the dump is not plain text - try using pg_restore -l your_db_dump.file
command. It will list all objects in the database dump (like tables, indexes ...).
Another possible way (may not work, haven't tried it) is to grep
through the output of pg_restore your_db_dump.file
command. If I understood correctly the manual - the output of pg_restore
is just a sequence of SQL queries, that will rebuild the db.