To = you aziztarin = dearest doostami = my friend "doost" is friend and 'mi' is the attached personal pronoun "my". The sentence structure is quite different.

You can say 'تو عزیزترین دوستمی ' or To aziztarin doostami

To aziztarin Doostami (تو عزيزترين دوستمي) Mi = MY doost = friend