Perhaps these links will help you find what you need:
Try also to search Malamud's name here at enotes.
I don't know how many novels and short stories Malamud wrote during his lifetime, but his career spanned more than thirty years, suggesting that his body of work is quite large. For you to review everything he wrote sounds like an enormous task, more suitable for a graduate thesis than for a single essay.
It also suggests that you will need to find sources of literary critical analysis that deal specifically with Yiddish in literature (and might include Malamud) and, if you can find them, sources that deal specifically with Yiddish in Malamud's work. This kind of research is so focused and specific, your best approach would be to use literary data bases found in college and university libraries.
If possible, limit your topic to address a few of Malamud's most well known works, instead of surveying everything he wrote.
Can you be more specific? Do you need examples of Yiddish words and phrases from his various works or from one work in particular? Do you need information about his work as to why it would include Yiddish words and phrases? What exactly are you seeking to learn?
There are several Yiddish dictionaries online. Here's one link I found that looks like it might be helpful because you can type in a Yiddish word or phrase and find the English equivalent.
Also, here are some enotes links that will take you to some interesting information about Yiddish literature and Bernard Malamud.
I have to write an essay on Malamud's use of Yiddish words and phrases. I need such examples from all of his works supported by critics' comments and citations
i need more information on malamud's use of yiddish words and phrases