I hope that you will enjoy to the fullest your last year of being in your thirties.
I hope you will have a blast spending the last year of being thirty-something.
ご質問ありがとうございます。
① "I hope that you will enjoy to the fullest"=「あなたが目一杯楽しめることを願っています」
"your last year of being in your thirties."=「あなたが30代の最後の年であることを。」
② "I hope you will have a blast"=「あなたがメチャクチャ楽しむことを願います」
"spending the last year of being thirty-something."=「30何歳でいる最後の年を過ごすのを。」
ご参考に。