If you can find a retail install disc on DVD or CD, that would be in consequential, otherwise there are rules.
When an older computer hasn't a Combo optical drive and can't directly use DVD media, you can sometimes work around that if the subject computer isn't too old (that one likely is) through use of another Mac that has the correct optical drive. Seems to me the iMac G3 first model had no FireWire, but later ones did.
The better bet would be to find a working later model Mac with at least FireWire and faster processor so Tiger 10.4 or better would be possible, or even a G4 Mini. Or a repaired iBook G4 last model. Depending on where you look these can be inexpensive. Some well-established Mac companies online do a fair mail order with older vintage hardware, and offer a guaranty.
Good luck & happy computing! 🙂