My input npy files are of size (101,150) and my (target)label npy files are (801,4). How should I feed this type of data to neural network?
your input matrix os of size(101,150) means the total element is 15150, but the Your NN is taking only 3204 elements as input. To solve this either you have to add an extra input layer in NN which has 15150 input nodes either you have to remove some features from the matrix. Depending on your input you can use Principal Component Analysis (PCA) Algorithm. It is sed to for dimensionality reduction. you can use numpy.shape() to reshape your input matrix.
Any information on how to resize the numpy arrays to be of same shape for training  would be very helpful.