Is this voice change correct?

Question

I have written a text about a motorbike. I would like to rewrite it converting into passive voice. I know how to do it grammatically. But I'm not sure the change I have made sounds right or not.

A few days ago, somebody stole Keith Dunn's motorbike. Keith had left his motorbike outside his house. Keith reported the theft to the police. The police told him they would try to find his motorbike. This morning, the police called Keith and asked him to go to the police station. They had found his motorbike. The thieves had painted it and then sold it to someone else. The new owner had parked the motorbike outside the police station. The police arrested the thieves.

And after voice change I rewrote the text as:

Keith Dunn's motorbike was stolen a few days ago. His motorbike had been left outside his house. The theft was reported to the police. He was told a police would try to find his motorbike. This morning, Keith was called and asked to go to the police station. His motorbike had been found. It had been painted by the thieves and then had been sold to someone else. The motorbike had been parked by the new owner outside the police station. The thieves were arrested by the police.

Answer 1

You can use one of the following:

He was told by police that they would try to find his motorbike.

He was told that the police would try to find his motorbike.

Police is treated as plural and usually "the police" but never "a police". If you were to refer to an individual police officer, then it would become an adjective to the noun officer, man or woman e.g.. a police officer; a policeman; a policewoman.