  In this study we demonstrate the application of the Maximum Entropy Method
(MEM) to determine the valence quark distribution of exotic hadrons. Our
investigation yields three key findings. Firstly, we observe a significant
shift towards smaller Bjorken scale $x$ in the peak position of the valence
quark distribution for hadrons with an increasing number of valence quarks,
consistent with previous results by Kawamura and Kumano. Secondly, assuming
that the $Z_c(3900)$ initially consists of four valence quarks, we employ MEM
to determine its initial valence quark distribution, estimating a radius of
$r_c=1.276$ fm at an extremely low resolution scale $Q^2$. Furthermore, we
identify a notable discrepancy between our computed charge form factor $G_c(q)$
at leading order and the outcomes of hadron molecular state calculations. We
propose that this form factor can be extracted from the QCD counting rule
cross-section, which is grounded in Generalized Distribution Amplitudes (GDA)
linked to the multi-quark states.
