How to I get into my Mac when my mouse and key pad not responding

If it's the new Apple wireless keyboard with a Lighting port, it will work as a wired keyboard if it's connected to the computer with its USB to Lightning cable.

Until the mouse is setup you could use Mouse Keys.

Control the pointer using Mouse Keys on Mac - Apple Support

Pressing the Option key five times should turn it on or off.

Change Alternate Control Methods preferences for accessibility on Mac - Apple Support