There are two ways in which African Americans have generally benefitted from mutual aid. However, neither of them can be explained in any quantifiable way. You cannot provide statistics that conclusively show how mutual aid was beneficial. The best you can do is to explain the mechanism by which mutual aid helped African Americans. You can also give anecdotes that might suggest (but not prove) the benefits of such aid.
Mutual aid helped African Americans in two major ways. First, it helped them in tangible ways. In the days before government welfare programs and before more widespread prosperity, mutual aid societies provided tangible benefits like insurance and burial benefits. In other words, people could get some of the material assistance that they needed from the societies. This helped make people’s lives somewhat easier and more secure. This, however, cannot be quantified in statistics. Second, mutual aid helped African Americans in intangible ways. It helped preserve a positive self-image for African Americans because it gave them a way to prove that they could help themselves. It also gave specific African Americans the ability to exert leadership and to develop their talents. This is something that can be shown though anecdotes. You can note that the leaders of the Civil Rights Movement had typically been leaders in the black church. You can identify black leaders who have been members of lodges. These sorts of anecdotes do not prove that mutual aid helped African Americans, but they do suggest that it did.
So, to explain this, you need to discuss the mechanisms by which mutual aid helped African Americans and then give whatever anecdotes you can to support your claims.