Question

we must look into this matter change the voice

Answer 1

Q. We must look into this matter. (change the voice).
Ans. This matter must be looked into by us.

Modal auxilary include 'must'. And while changing the voice of modal auxiliaries, we have to use 'MA + be'.

Hence, the answer is, - 'This matter must be looked into by us'. With C.V. structure- obj + must + be + sub + ow.