There is a history Kubernetes Engine -> Workloads and click the CronJob name.

If you cannot see it that might indicate your Job was scheduled just once.

Of course you can also check using kubectl command

$ kubectl get cj
NAME    SCHEDULE    SUSPEND   ACTIVE   LAST SCHEDULE   AGE
hello   * * * * *   False     1        7s              4m7s


$ kubectl get jobs
NAME               COMPLETIONS   DURATION   AGE
hello-1563535260   1/1           2s         2m16s
hello-1563535320   1/1           1s         76s
hello-1563535380   1/1           1s         15s