I’m trying to merge my contacts from iPhone to iPad. When I turn on Contacts on iPad, no pop-up to Merge. What am I doing wrong?

Are both your iPad and iPhone signed-in to iCloud with the same AppleID?

If not and you intend to use a single AppleID account, you will need to sign-out on the device(s) that you intend to change AppleIDs.

When you sign-out, you’ll be presented with the option to download and save a copy of your information stored in iCloud. If you intend to merge this data, select save a local copy. If you do not intend to merge the data, do not save.

Having signed-out of iCloud, you’ll then be able to sign-in to iCloud with the desired AppleID; when you do so, data saved during the previous sign-out will be automatically merged with the new AppleID account.

I had this issue yesterday. I went to both my iPhone and iPad and turned them off and on. Also, make sure you have enough storage in your iCloud.