How to convert process / cpu core based upon MIPS?
For a modern CPU there is no exact MIPS rating since it depends on the specific instruction stream, power saving mode, and other factors. As a reference number you may look at the BogoMIPS rating that is calculated by the Linux kernel.

A desktop CPU core at 3GHz can process about 2 instructions per clock cycle on average resulting in a rating close to 6000 MIPS (or 6 billion instructions per second), therefore 18 trillion instructions would require about 3000 cores.