I have a full-time job and two part-time jobs. Do I need to make MPF contributions in the part-time jobs if I have already made MPF contributions in the full-time job?

It depends on the employment period and the relevant income of your part-time jobs. If the employment period is more than 60 days, you are required to join the MPF scheme of respective employer. However, if your income is less than HK$7,100, you do not need to contribute but your employer does.