does this require a B566 terminal base to connect to midi GL 840?

Yes, the B-564 requires the B-566 terminal base as well as a B-567 connection cable.

If you are adding a B-564 to a GL840 you actually need two of the B-566 terminal bases.  One for the  existing terminal block and another for the additional one.

We actually sell all this as a kit here - https://microdaq.com/graphtec-gl840-m-20-kit.php