Assuming dates are always in either of these two forms
MMM D, YYYY or MMM DD, YYYY
then this should work
=MID(A1,5,SEARCH(",",A1)-5)&"/"&LEFT(A1,3)&"/"&MID(A1,SEARCH(",",A1) +2,4)
if the month varies in length then this should work
=MID(A1,5,SEARCH(",",A1)-5)&"/"&LEFT(A1,SEARCH(" ", A1)...