Renumber table rows

Hello.

I have a table that his primary key is not ordered is something like this:

1 - a
12 - b
123 - c
etc.

I want to do an update to make it like this

1 – a
2 – b
3 – c

I tried this:

UPDATE operador SET idoperador=(SELECT row_number() OVER (ORDER BY idoperador) from operador)

But it returns this error: more than one row returned by a subquery used as an expression and I know that is because the substring returns more than one row, but how can I use the subquery to perform the update?.

Thank you in advance