Frankly, if you have no knowledge of electric, please don't play with live voltage or diy. These things kill. If it not wired properly you may end up shorting people pressing the bell.

Usually doorbell (in malaysia) already have the small transformer inside, which it will be connected to outside switch, once the door bell press, it will complete the loop. If not press it will not waste any energy.

Use different region device without knowing how the current one work, the wireman sure will not want to touch it. Any issues is the wireman issues.