How to add a field if the string matches a word in message

[Guhan_S]

{"level":30,"time":1605686969640,"pid":1,"hostname":"ip-100-91-70-500","name":"ZA-dev",
this is my sample logs,
here i am trying to achieve, if level:30 in message it has to create info log-level,
i tired
filter {
if [level] == "30" {
mutate { add_field => [ "log-level", "info" ]
}
}
}
but not getting correct requirement. i am new to elk, can someone please tell me how to achieve this

[Badger]

If the [message] field is valid JSON then you could use a json filter to parse it

json { source => "message" }

You will then have a [level] field that you can test

if [level] == 30
    ...

[Guhan_S]

thanks man, its works.