I am going to assume that you have the Beige G3 and not an iMac G3.
The operating system you should be looking for is OS 9.2.2
I would say that you should look toward OS X but in its original configuration it was a little sluggish for 10.2.x (Jaguar) which is as high as you can go with the Beige G3
Any of the Mac mail order catalogs, MacMall/CDW/MacZone/etc. will be able to fix you up with a copy of it. You can even buy it from the Apple store. The copy you get on CD may not be 9.2.2 but it will be close enough and you can upgrade the system to 9.2.2 from there.
Depending on what programs are already on the machine and what programs you have CD's for, will be the deciding factor on what sort of install you do. "Clean Install" on a Mac does NOT entail formatting the drive. It just puts a virgin copy of the OS onto the drive and all the applications and files are left intact.
If you are happy to destroy all the apps on the machine, you should initialise the drive (like a format only quicker) and then install OS 9.x
Once installed and configured, you should update the OS to 9.2.2 .These are free downloads from Apple.
Oh, BTW, to see what OS is currently on the machine, go to the Apple Menu (Top left of screen) and select "About this Computer" (If the system is old, it may say "About this Mac")
If you need to know anything else, just holler
Hope this all helps
im not familer with apple computers and i just puchased a power mac g3 power pc i need to know what version of apple operating system it has so i can buy a recovery disc. it works fine but all of the old owners files are on it and i just want to do a clean install.