Student or Learner
What parts of sentences did you need to change in order to shift number?
That was the question, I just wanted to know what kinds of parts of sentences are there? And what does what part mean? (But I think what kinds of parts of sentences would already answer my question)
The expression 'parts of sentences' would normally refer to either clauses or phrases.
Without further context, it would be impossible to say which was meant in this case.