Question

The children will have made toys.possive voice

Answer 1

Toys will have been made by children.

Answer 2

1 u should interchange the subject and object from their places

2 tense change
the sentence is in future perfect now change to will/shall + have + been + past participle format

make - made - made

3 now add the prepositional agent by

answer:

toys will have been made by the children