Q: My old computer a POWER PC, mod G4 (2/10/04) running OS 10.5.8

You will need to expand on what you want to do.

State what you wish to accomplish.

Do you mean to copy your files from your old computer to your new computer?

The easiest way would be to copy the files on a flash drive.

http://www.microcenter.com/single_product_results.phtml?product_id=0281032

Robert