The Kubernetes version 1.16.0 stopped to serve the following deprecated APIs:

1. NetworkPolicy (in the extensions/v1beta1 API group):
   Migrate to use the networking.k8s.io/v1 API, available since v1.8. Existing persisted data can be retrieved/updated via the networking.k8s.io/v1 API.

2. PodSecurityPolicy (in the extensions/v1beta1 API group):
   Migrate to use the policy/v1beta1 API, available since v1.10. Existing persisted data can be retrieved/updated via the policy/v1beta1 API.

3. DaemonSet, Deployment, StatefulSet, and ReplicaSet (in the extensions/v1beta1 and apps/v1beta2 API groups)

You must check your older YAMLs. But changing the listed parameters in all files can be an exhausting task.

An option would be to convert the older files.

For example, lets deploy a NGINX using the file nginx.yaml.

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
 labels:
 run: nginx
 name: deploy-nginx
spec:
 selector:
 matchLabels:
 run: nginx
 template:
 metadata:
 labels:
 run: nginx
 spec:
 containers:
 - image: nginx
 name: nginx

The files nginx.yaml sets apiVersion: extensions/v1beta1 and it's compatible with kubernetes older versions, but not run on The last.
To convert the older YAML, using client 1.16 execute kubectl with the option convert:

kubectl convert -f nginx.yaml

Command screen output would be like:

apiVersion: apps/v1
kind: Deployment
metadata:
 creationTimestamp: null
 labels:
 run: nginx
 name: deploy-nginx
spec:
 progressDeadlineSeconds: 2213489811
 revisionHistoryLimit: 2213489811
 selector:
 matchLabels:
 run: nginx
 strategy:
 rollingUpdate:
 maxSurge: 1
 maxUnavailable: 1
 type: RollingUpdate
 template:
 metadata:
 creationTimestamp: null
 labels:
 run: nginx
 spec:
 containers:
 - image: nginx
 imagePullPolicy: Always
 name: nginx
 resources: {}
 terminationMessagePath: /dev/termination-log
 terminationMessagePolicy: File
 dnsPolicy: ClusterFirst
 restartiPolicy: Always
 schedulerName: defaul-scheduler
 securityContext: {}
 terminationGracePeriodSeconds: 28
status: {}

Paste the command output to a file(ex: nginxOUT.yaml)

kubectl convert -f nginx.yaml > nginxOUT.yaml

Deploy

Using output file

kubectl create -f nginxOUT.yaml

Directly with the older file

kubectl convert -f nginx.yaml | kubectl create -f -

References

https://kubernetes.io/blog/2019/07/18/api-deprecations-in-1-16/