my niece has a 1.8l toyota corolla and its showing a cylinder 1 misfire(301)code

You need to get the firing order to pin point the issue to a certain plug, but good rule of thumb is change the wires when you change the plugs. If this doesnt work change the coil.

GET DIAG AND EST AS TO WHAT IT IS,IT COULD BE MANY ISSUES

Swap the coil from #1 to #3 and see if the misfire follows the coil ,if it does , then replace the bad coil.