Mate o porto npm
npx kill-port 3000
Jittery Jackal
npx kill-port 3000
lsof -i tcp:3000
//look under PID, the number that appears is the process you want to kill. You can do so as shown bellow. Make sure you remove the '<>'
kill -9 <number> sudo pkill nodetaskkill /f /im node.exelsof -i :3000
kill -9 <PID>