I'll be as quiet as a mouse.
→  쥐 죽은듯 조용하게 있을께.

[예문]
quiet as a mouse :아주조용한, 쥐 죽은듯이 조용한.

A: Don't make any noise. The baby's sleeping.
아무소리내지마. 아기가 자고있어.

B: Don't worry. I'll be as quiet as a mouse.
 걱정마., 쥐 죽은듯 조용히 하고있을께.