Question

i knew him very well what its passive voice

Answer 1

He was known to me very well.

Hope it help u.....

Answer 2

$\huge\boxed{\underline{\mathcal{\red{A}\green{N}\pink{S}\orange{W}\blue{E}\pink{R}}}}$

$\dashrightarrow$He is known to me very well .

or

$\dashrightarrow$He known very well by me .