About 40%, slightly less of Dearborn is Arab, slightly less. Arab does not mean Muslim, although it is more common there, as a lot of the Christian Arabs (majority in Michigan) are in Oakland or Macomb County. Dearborn has about 100,000 people. It's now 5% black, (was none for years as they used to have a segregationalist mayor). It's mostly white ethnic. Dearborn is about 30% foreign born, that includes some of the Poles and Italian immigrants.
Hamtramck total has 20,000 people. Mostly Albanian, East Indian, Bangledeshi, or black along with still some Poles, although their numbers are declining.
Overall Michigan is about 1-2% Muslim. It's overwhelmingly Christian. So if you strictly take Dearborn and Hamtramck's population of Muslims, it's maybe 40,000, in a state of 10 million people. Most Muslims here are black.