How do you translate my dear rabbi from English to Hebrew?

Answer 1

If the rabbi is male: rah-bee ha-yah-kar (רבי היקר)
If the rabbi is female: rah-bah-nee-tee ha-yeh-kah-rah (רבניתי היקרה)

Many (possibly most) female rabbis prefer the word Rav over Rabanit, so for female rabbis, you could also say: rah-bee ha-yeh-kah-rah (רבי היקרה)

Answer 2

• If the rabbi is male: rabí ha yakár (רבי היקר)
  
• If the rabbi is female: rabanití ha yekará (רבניתי היקרה)*

*Note: Most female rabbis prefer the word Rav over Rabanit, so for female rabbis, you could also say: rabí ha yekará (רבי היקרה)