Let's transform the given sentence using the provided keywords:

1. **Unless**:
- Original: "If I study hard, I will pass the exam."
- Transformed: "Unless I study hard, I will not pass the exam."

2. **So**:
- Original: "If I study hard, I will pass the exam."
- Transformed: "I need to study hard so that I will pass the exam."

3. **Should**:
- Original: "If I study hard, I will pass the exam."
- Transformed: "Should I study hard, I will pass the exam."

Each transformation maintains the original meaning but uses the specified keyword to convey the same idea.