I have UWin version of Unix for Destop

I have files with extension *.abc. I want to rename it to *.csv.
Some of the filenames have spaces.
I also to rename the files with extension *.abc in the corresponding subfolders
ex
==
abc def.abc
ghi jkl.abc
mnopqr.abc
uvwxyz.abc

rename as
========
abc def.csv
ghi jkl.csv
mnopqr.csv
uvwxyz.csv

Well I solved it myself after few tries

ls -ltR | awk '{print $9}' | sed 's/abc/csv/g'

That will change what is displayed to the screen, but doesnt actually rename any actual files.

Thanks for pointing out.
How do I actually rename it.

Here is a link with some ideas on how to handle this:

Batch change extension of files on the unix command line