This import file is an export done with a tool such as exp73, exp or expdp.
The manner of importing data you are referring to when you have data in an excel sheet with coma separated value, SQL developer will create a large insert statement with the data for you and run it, which will populate a table.
What you want to do is to use oracle import tools such as impdp or imp.
Do you happen to have the export's log ? There might be a file with the same name that finishes with a .log
Here is an example of syntax on how to import specific tables of an Oracle export
impdp username/password@oracle_sid tables=table1,table2 directory=data_pump_dir dumpfile=dumpfilename.dmp logfile=import_exec_log.log
You will want to run the following query to find where your data pump dir location is and place the export in the corresponding folder :
select * from dba_directories where directory_name ='DATA_PUMP_DIR';