You do not need to do anything from scratch! You will get credit on some of the hours you already have. If you want to get the CPL cheaper then go the modular way. But you will have to redo the exams and do some solo/ dual hrs and of course the checkride.
Best would be to contact Some flight schools and seek their advice. I know personally someone who converted MPL to CPL. It’s not impossible however with Current travel restrictions It will take you some time.