Sign in to the same Apple ID on both iPhone and iPad
On iPhone, open Settings
Tap your name at the top
Tap iCloud
Turn on Contacts
On iPad, open Settings
Tap your name at the top
Tap iCloud
Turn on Contacts
Make sure both devices are connected to Wi-Fi
Wait a few minutes for contacts to sync
If needed, open the Contacts app on iPad and refresh the list
If contacts still do not appear, check that Contacts is enabled under iCloud on both devices
If needed, restart both devices
If needed, sign out of iCloud and sign back in on both devices