How to use titles instead of IDs in urls for nodes?
You should check to see if the pathauto module is installed. If not, I highly recommend downloading, installing and enabling it... It should make very short work of this.

Here's the link for d6

https://www.drupal.org/node/17345/release?api_version%5B%5D=87

If it is already enabled... then you may have more trouble as the d6 version is no longer maintained... so you may need to do some troubleshooting of this module.