I have 3000 contacts in my iphone but only 500 in icloud. Someone can help me ?

Contacts sync to email servers. So many of the contacts in your phone come from an email account other than iCloud. You would have to move the contacts from servers other than iCloud to the iCloud “list” in your Contacts app. If you have a Mac and you have the same email accounts on your Mac that you have on your phone this is easy; you can use the Mac Contacts app and just drag the contacts that are not iCloud to the iCloud list. The other alternative on your iPhone is with a 3rd party app such as Groups.

See the following Apple Support article for information on iCloud contacts not syncing. A frequent reason is that some contacts are set as 3rd party (Google, Yahoo, etc) rather than iCloud but the following support article covers that as well as other reasons: What to do before you sell, give away, or trade in your Mac - Apple Support