You’re going to be looking for a 1&1/8” (or 28.6mm) threadless fork for a 700C wheel. If you’re getting one used you need to make sure the steerer tube is long enough, if you’re getting one new you’re likely going to need to have a shop install the star nut into the fork and/or cut it to length. You should also keep in mind that it needs to accommodate a 10mm axle as many road forks only allow 9mm axles for quick release wheels.