set pages 9999
spool map.lst
col FILE_ID print
col BLOCKS print
col BLOCK_ID print
col FILE_ID format 999 head "file"
col EXTENT_ID format 999 head "ext"

select owner,SEGMENT_NAME,TABLESPACE_NAME,EXTENT_ID,FILE_ID,
        BLOCK_ID,BYTES,BLOCKS
from dba_extents
where tablespace_name = ('whatever tablesapce you want')
UNION
select '-','free',TABLESPACE_NAME,0,FILE_ID,BLOCK_ID,BYTES,BLOCKS
from dba_free_space
where tablespace_name = ('whatever tablesapce you want')
order by FILE_ID,BLOCK_ID
/