Don't conflate the two I assume you mean Arab Muslim voters. Sanders did well with Arab Christian voters(presumably) but not so well with black and probably South Asian Muslim( though I'm not 100% sure) voters
He did well with black Muslim voters such as Somalis in Minneapolis. Less certain about South Asian Muslims.
Are you talking about the Nation of Islam cultists?
A few decades ago it was true that most African-Americans who claimed the Muslim faith followed the "Nation of Islam". Estimates have suggested that at its peak in the '60s and '70s, the NoI held sway over some 250K African-Americans (about 1.5% of the Black population).
After that point, though, membership in the NoI dropped heavily as major figures in the NoI such as Muhammad Ali and Malcolm X reverted to mainstream Sunni Islam and as the last leader of the original NoI, Wallace Muhammad, increasingly aligned the NoI away from many of its more heretical teachings. He disbanded the original organization in 1986.
Most people in the original NoI eventually either have become Sunni Muslims or have returned to Christianity. There was a splinter group led by Louis Farrakhan which today has become the dominant replacement for the NoI, but it never quite caught on as much as the original. Farrakhan's NoI was estimated to have 50,000 members as of 2007, much smaller than the total number of Black Muslims in the U.S., at approximately 700,000.
I suspect (based on anecdotal evidence, no hard data to back this up, unfortunately) that Black Muslims mainly supported Clinton and Biden, but at slightly lower levels than Black Christians.
