There must be a word missing after protestant. If it’s referring to a church it should be Protestant. You can’t have ‘reunification’ with ‘conversion’.

I'd assume it means hoping for two things: 1. reunification with protestant and 2. the jews' conversion. It would be easier to say with more information though. This fragment is a bit short. As for why 'protestant' and not 'protestants', really impossible to beat without being able to read the wider passage. Maybe a typo?