Could someone tell me the MANN part # for a transmission fluid filter for a 1983 300D turbo diesel 4 door sedan ?

 

I would try going to the Mann internet site.
See if you can click on Catalog; from there they may have a way to look up the Filter you need by application (the make, model and year of your vehicle).
If they do not have a list of filters by application they often have an interchange where you can put in an other Competitor's filter number and it will give you the Mann number.

 

I believe the number is H2014 (Mann filter)