Pentium-4 is a very old architecture (almost 10 years now). I wouldn't invest any money on such an old system. You should get a new PC or just keep using the old one as it is if your current motherboard is still functional.
The first Pentium-4 supported RAMBUS and after that they switched to DDR1. So I don't think you'll find a motherboard that support your socket combined with DDR3. But just out of curiosity, why do you want to replace your motherboard and why do you want DDR3? That CPU is so slow that it probably won't be able to take advantage of DDR3 even if you find a motherboard that supports it.