Sign in to the same Apple ID on both iPhone and iPad
On iPhone, go to Settings
Tap your name
Tap iCloud
Turn on Contacts
On iPad, go to Settings
Tap your name
Tap iCloud
Turn on Contacts
Make sure both devices are connected to Wi-Fi
Wait a few minutes for contacts to sync
Open the Contacts app on iPad to check the synced contacts
If needed, turn Contacts off and back on in iCloud on both devices
Make sure Contacts are selected in the iCloud account on both devices
Restart both devices if contacts do not appear
Check that iCloud storage and internet connection are working properly