Help set up averaging

Hello! I cannot figure out the averaging function

B=rand(200,3000);
bp=maen(B,5) % need to average 5 values ​​in each column

% I need to get a 40x3000 matrix

Answer 1

[KSSV]

https://in.mathworks.com/matlabcentral/answers/80480-how-do-i-take-the-average-of-every-n-values-in-a-vector

[Lev Mihailov]

I did as in the answer and decided to crank up the operation to create a matrix, I just need a matrix with averaged values

Avg1=reshape(Avg,40,3000);
Error using reshape
To RESHAPE the number of elements must not change.

how do I render my matrix from a vector again?