Your issue is self explanatory - you have declared parameters @d6, @d7 & @d8 but have not added them to your SQL Command prior to executing the query.
If you were to get past this first error - perhaps by setting the values to NULL, then you would get a similar error when you get to your second insert but the error would be "Must declare the variable @d1"
if you wanted to set the values to NULL in the respective insert statements you would do as follows;
cmd.Parameters.AddWithValue("@d6", DBNull.Value)
Alternatively have 2 different Insert statements