My contacts are different on my iPad and my iPhone. Using ICloud to sync between them (and Mac). Any suggestions?

My iPhone contacts are different from my iPad and Mac. Going to iCloud on them hasn’t worked, it says they are already connected. I’m finding out contacts that I need on my iPhone aren’t there, but can find them on my iPad. Can’t merge or link them.

I also have the same problem with mail between my devices. My iPhone will say I have a total of 300 emails on all email accounts, my iPad will say 900. My Mac is a whole different story, it says I have 1000+. When I go through my emails and delete some, it’s not showing up on the other devices. Plus now my email goes back to 2013!

Thank you!