Unlike the US, in Europe you need a type rating to act as first officer in all multi crew planes (except some small ones such as King airs which are flown single crew and you act as pilots assistant but do not log time.)
If you have no jet time, as well as the rating done at one of the above training organisations you would need to find an airline willing to do the base training for you in the actual aircraft.
There are a few 737 ones on offer but I have not seen any 757/767 ones advertised.
Most operators want time on type as well as the rating if they don't train you themselves though with 6000 hrs turboprop you might be lucky with just the rating.