How can we clean up/backup of .DBF files in Oradata folder in ORACLE on windows
In general Oracle doesn't make it easy to reclaim disk space, other than through cleaning up log and trace files. If you haven't already, consider rotating the listener and alert logs, or removing old trace files from the ADR subdirectories. If you have much free space within your data files, also consider reorganizing your tablespaces (online reorg of tables, rebuiling indexes) to defragment them, then attempting to shrink your data files.
These articles - Automatic Diagnostic Repository (ADR) in Oracle Database 11g Release 1 (ADRCI) and Reclaiming Unused Space in Datafiles - will help you get started.